Immersing in Lesson Study in Japan: International Educators Learning Through Cross-Cultural Observation

Abstract

This study examines how international educators come to understand Lesson Study as a form of professional learning through participation in the Lesson Study Immersion Program in Japan (LSIP-JR). While prior research has documented the impact of Lesson Study on individual teachers’ knowledge and instructional practices, less attention has been paid to how teachers recognize the norms of learning communities and how they conceptualize curriculum and instructional tasks as objects of collective inquiry. Drawing on reflective journals produced by program participants, this study analyzes how these often-implicit dimensions of Lesson Study were interpreted through engagement with Japanese classroom practices and professional learning discourse. The findings suggest that participants did not view research lessons as polished demonstrations but rather as provisional inquiries shaped by uncertainty, shared responsibility, and openness to critique. Such interpretations brought into focus norms that are deeply embedded—and often taken for granted—within the Japanese educational context. In addition, participants came to recognize curriculum materials and instructional tasks not simply as tools for implementation but as shared research objects through which hypotheses about student learning are generated and examined, within both normative and institutional conditions. Rather than presenting Japanese Lesson Study as a model to be replicated, this study clarifies the conditions under which Lesson Study functions as collective inquiry. By making these typically unarticulated elements visible, the study offers a conceptual foundation for teachers and professional development leaders seeking to design and sustain meaningful Lesson Study across diverse educational contexts.

1. About the Research

1.1. Limitations of Traditional Professional Development (PD)

Despite decades of educational reforms, research has consistently shown that traditional PD, which is generally characterized by occasional, lecture-based workshops in which teachers passively listen to experts, rarely leads to sustained improvement in teaching practice. Empirical and theoretical work has questioned the effectiveness of such approaches, particularly in supporting teachers’ learning that affects students’ learning (e.g., Gersten et al., 2014; Darling-Hammond et al., 2017; Banilower et al., 2018; Popova et al., 2022).

From the perspective of adult learning theory, traditional PD formats have been widely criticized for their limited impact on teacher learning. Trotter (2006) found that such approaches often neglect the principles of adult education, which emphasize autonomy, experiential learning, and critical reflection. This critique aligns with Mezirow’s (1991) and Cranton’s (1992) theory of transformative learning, which positions teachers not as passive recipients of assigned or transmitted content but as actively engaged professionals who transform their prior understandings through experience. This theoretical critique is supported by multiple reviews of empirical research, which conclude that concrete, practical, and classroom-based PD programs are highly effective for teachers’ professional growth (Darling-Hammond et al., 2009; Walter & Briggs, 2012; Popova et al., 2022). Furthermore, Darling-Hammond et al. (2017) reviewed 35 high-quality PD studies, identified seven core features of effective PD, including content focus, active learning, collaboration, modeling of effective practice, expert support, reflection, and sustained duration, underscoring the need for PD that is interactive, practice-based, and responsive to teachers’ professional contexts.

Kennedy (2016) critically examines the assumption that specific design features—such as a focus on content knowledge, collective participation in professional learning communities, program intensity, and the use of instructional coaches—automatically lead to improved teaching. She explained that mandated PD often fails to produce meaningful learning, noting that programs involving voluntary participation yielded significantly higher effects. According to the U.S. Institute of Education Sciences, only two out of 643 mathematics professional development programs have been shown to produce statistically significant positive effects in student achievement, and the Lesson Study was one of them (Gersten et al., 2014). This finding strongly suggests that approaches based on collaborative engagement rooted in classroom practice and teachers’ needs about the curriculum contents are particularly likely to be effective for students’ learning.

Stigler and Hiebert (2009), based on their findings from a large-scale international survey, TIMSS Video Study, argued that “Listening to experts during special professional development days does not translate into improved teaching. Effective teacher learning must be built into teachers’ daily and weekly schedules. Schools must become the places where teachers, not just students, learn.” This perspective requires reframing professional learning as an ongoing, collective responsibility rather than an isolated event. This reconceptualization of schools as sites of teacher learning is also emphasized in recent international policy discourse. The OECD Teaching Compass shaped teachers’ role directions as “not only enablers of student learning, but also active participants in their own learning journeys (OECD, 2025, p. 10)”, who are actively engaged in their own learning process.

Taken together, these theoretical perspectives, empirical findings, and policy frameworks point to the need for a fundamental shift in how PD is conceptualized. Stigler and Hiebert (1999, 2009) highlight the cultural contrast between U.S. and Japanese teaching practices, arguing that the quality of instruction is deeply influenced by whether teachers are embedded in a culture of continuous, collaborative learning. Their comparative analysis underscores the importance of designing PD that is not episodic but integrated into the daily routines and professional communities of educators, such as Lesson Study.

1.2. Lesson Study as a Teacher-Driven Continuous Professional Development

So, what forms of PD exist that empower teachers as the active agents of their own learning? One widely recognized example is Lesson Study. Lesson Study is a unique PD system with a self-improvement function, where teachers cultivate their own professional growth through its entire process by themselves (Fujii, 2014). The key difference between traditional teacher training or workshop-style PD and Lesson Study is that the former begins with content presented by an instructor as “the correct answer,” while the Lesson Study starts with questions posed by the teachers themselves (Lewis, 2002; Fujii, 2014, 2016; Takahashi & McDougal, 2016; Shimizu, 2019). In the process of Lesson Study, based on analysis of student realities and the desires of the team, a “research theme” is clearly defined. Under this shared theme, a Lesson Plan serving as a “research proposal” will be developed. Therefore, the subject of teachers’ inquiry is the research lesson itself. Right after the research lesson observation, post-lesson discussions are conducted based on various data collected from observers, and then external instructors, called “knowledgeable others” or “Koshi”, make final comments to guide their further research.

However, various forms of initiatives called “lesson study” are implemented worldwide currently. Therefore, the reality is that understanding and actual practice of Lesson Study are remarkably diverse (Fujii, 2014; Huang & Shimizu, 2016). Consequently, it is reasonable to expect that the effectiveness and sustainability of Lesson Study also range widely. In Seleznyov’s (2018) review of academic papers on the implementation of Lesson Study, it is noted that many papers report outcomes related to teachers’ knowledge and beliefs as a result of Lesson Study. In contrast, reports on other areas, particularly the impact on students’ long-term learning, are extremely limited.

1.3. Theoretical Perspectives and Research Gaps in the Research on Lesson Study

Lewis (2016) and Lewis et al. (2019) have proposed a theoretical framework that aims to provide a more comprehensive understanding of the potential impact of Lesson Study. Furthermore, Lewis et al. (2022) conducted a study examining three U.S. schools that have demonstrated clear impacts on student learning and have effectively established and sustained school-wide Lesson Study. Their findings identified the characteristics in these schools, including teacher agency, which is the first major theme that emerged from the data. It is about how teachers were working as key agents to set the school research theme, choose the curriculum unit to study based on their authentic questions and concerns, and so on.

On the other hand, according to a literature review by Ding et al. (2024), which used Lewis’s (2016) theoretical model as a framework and examined recent research on Lesson Study, including in Japan, it has been revealed that among the pathways influencing student learning, empirical reports related to the impact on “curriculum” and “teacher learning communities (norms and culture of learning)” remain particularly limited. Thus, while Lesson Study has much evidence supporting its effectiveness as PD that influences individual teachers’ knowledge and beliefs, some key factors that impact students’ learning remain insufficiently examined. To clarify this point, it is necessary to examine practices in schools where Lesson Study is carried out effectively in terms of students’ learning.

Given this existing research, it can be argued that the effectiveness of Lesson Study should not be limited to examining changes in individual teachers’ knowledge and beliefs but must be extended to verify its impact on more structural and cultural aspects, such as changes in the norms of the learning community and perspectives on the curriculum, or instructional tools and tasks. However, within Japan, Lesson Study is a traditional activity deeply rooted in the culture of teachers within schools, existing almost like the air itself. This makes it difficult for participating teachers to consciously recognize and appreciate it. As a result, teachers who lead their Lesson Study in a school or district may often engage in decision-making to design the annual plan and facilitate it without being consciously aware of key factors. On the other hand, outside Japan, it is often reported that it is institutionally and culturally difficult to sustain Lesson Study over the long term within school settings, making it challenging to verify its impact in the context of actual classrooms.

1.4. Observing Lesson Study: About the Lesson Study Immersion Program

To offer education researchers and in-service teachers opportunities to observe first-hand this uniquely Japanese PD system and to deepen their discussion of effective Lesson Study, International Math-teacher Professionalization Using Lesson Study (IMPULS) has organized “Lesson Study Immersion Program” in Japan (LSIP-J) since 2012. Since then, 443 participants from 16 countries have taken part in in-person sessions. As stated above, the centerpieces of the LSIP-J program are the observations of research lessons and post-lesson discussions. For a more detailed discussion of the design principles of the program, please see Takahashi et al. (2023). As Matsuda and Lewis (2016) discussed, the program participants learned about Lesson Study and deepened their understanding of mathematics content and children’s mathematical thinking.

However, due to the worldwide pandemic, the in-person program was canceled from 2020 to 2022. During that period, the IMPULS organized online programs (LSIP-O), making use of previously recorded research lessons and their post-lesson discussions. Takahashi et al. (2023) examined the learning of online program participants and found that their learning was similar to that of participants who participated in the in-person programs. Their analysis identified some features of the online programs that made such learning possible. Yet there were aspects of the in-person programs, such as embodied dialog and spontaneous interaction, that could not be replicated online.

Based on the experience of designing LSIP-O, the face-to-face program was redesigned. The number of mathematics research lessons observed has been halved from eight or nine lessons to four or five lessons, and more time has been allocated for pre- and post-lesson discussions. The redesigned Lesson Study Immersion Program in Japan (LSIP-JR) has been offered since 2023. This study seeks to examine how international educators engage with and learn from LSIP-JR, with particular attention to shifts in professional perspectives and assumptions about Lesson Study.

Unlike existing research on Lesson Study, which focused on “self-implemented Lesson Study,” this study focuses on a new learning format: “observing others’ Lesson Study.” Building on prior evidence of Lesson Study’s effectiveness, this study systematically analyzes self-reported transformations among LSIP-JR participants to characterize patterns of change and the specific triggers that precipitate them, thereby providing empirical nuance and complementary validation of existing findings.

The unique features of LSIP-JR are as follows:

• Intensive cross-cultural immersion: Participants leave their workplace and home country for a 10-day period, free from their daily duties, to participate in the program in Japan. Facilitators with experience living in both Japan and the U.S. and in supporting professional learning both for pre- and in-service teachers, provide support for this cross-cultural immersion.
• Mathematics Research Lesson Observation: Participants observed four or five mathematics research lessons, rather than regular classroom lessons. They were provided with translated lesson plans at least a day before and had opportunities to study the intent and structure of the lessons, both with the program facilitators and among themselves. After the observation, the program provided the time for them to share their observations and discuss their questions.
• Live Classroom Observation: Participants could move around the classroom with some freedom, albeit within limits, allowing them to directly observe student data. Simultaneous translation from Japanese to English was also provided by a bilingual translator.
• Fishbowl Observation: During observation, participants step back and observe Japanese teachers within the same classroom space, observing the research lesson and discussing it. Participants do not join the post-lesson discussions with Japanese teachers but observe the Japanese teachers’ discussions in a fishbowl-style setting. Subsequently, participants engage in a debriefing to exchange insights gained from the observation and their own reflections.
• Participant-driven Open-ended Format: Daily activities are flexibly designed according to participants’ interests and concerns. The goal is not to acquire predetermined knowledge or skills but rather to set one’s own questions and engage in individual and collaborative inquiry over the ten days.

LSIP-JR situates itself within a unique domain of learning, characterized by externally observing teachers’ PD processes in other educational cultures. It undertakes intensive short-term engagement and establishes structured opportunities for collaborative interpretation of mathematics lessons. Previous research on teachers’ learning through lesson observation, particularly in the field of teacher noticing (Sherin, 2007; Sherin & van Es, 2009; Jacobs et al., 2010), has focused on educators observing their own and their colleagues’ lessons within a common context. Furthermore, while there is abundant research on teachers’ PD in various national and regional programs, LSIP-JR is one of the few PD programs that focus on observation of Lesson Study as a core element of its design.

The program’s structure reflects this premise. Immersion here means more than physical presence in a Japanese school: it is sustained and intentional exposure to cultural patterns, collegial interactions, and the institutional systems sustaining Lesson Study. Participants observe live research lessons alongside Japanese teachers and then observe and listen to post-lesson discussion (PLD) among Japanese teachers. This deliberate arrangement for international educators to observe research lessons and PLDs in a fishbowl style enables them to listen to and interpret the discourse of Japanese teachers and knowledgeable others, compare these perspectives with their own, and cultivate professional vision or the socially organized ways of seeing (Goodwin, 1994). This fishbowl observation approach extends beyond noticing and interpreting the lesson itself to noticing and interpreting Lesson Study as a practice.

There are two structural elements that distinguish LSIP-JR from common PD formats. First, it shifts the focus from doing Lesson Study to observing it in authentic form, encouraging meta-cognitive reflection on both classroom practice and the processes of collaborative interpretation. Second, it embeds dedicated time for international participants’ own collaborative interpretation before and after observing research lessons and PLDs sessions that are central, not optional, in the program design. In these ways, LSIP-JR creates structured occasions for participants to identify existing knowledge developed through listening or reading. It enables them to see differently and deepen both pedagogical insight and cross-cultural professional understanding.

1.5. Research Question

The purpose of this study is to examine how participation in an immersion program influences teachers’ understanding of Lesson Study as a form of professional learning practice. Prior research has documented the effects of Lesson Study on teachers’ individual knowledge, beliefs, and instructional practices. In contrast, relatively limited attention has been given to how teachers come to understand the norms of professional learning communities and how they conceptualize curriculum and instructional sequences as objects of collective inquiry. These dimensions are a potential pathway to affect students’ learning through Lesson Study (Lewis, 2016), yet they remain underexamined.

To address this gap, this study investigates teachers’ learning through the LSIP-JR, designed to allow participants to observe first-hand key processes of how Japanese teachers work through their Lesson Study in a partial yet immersive, recursive, and intensive way. Research questions guiding this study are:

Research question 1 (RQ1):

How do participants come to understand Lesson Study as a form of professional learning practice through participation in LSIP-JR?

Research question 2 (RQ2):

How does participation in LSIP-JR influence participants’ perceptions of the norms of the learning community of Lesson Study?

Research question 3 (RQ3):

How does participation in LSIP-JR influence participants’ perceptions of the curriculum materials, instructional tasks, or instructional sequences as objects of inquiry?

RQ2 and RQ3 function as analytic lenses through which the overarching research question (RQ1) is examined. By addressing these sub-questions, this study identifies which aspects of LSIP-JR experience support teachers’ understanding of Lesson Study as a professional learning practice and offers implications for the intentional design of learning environments that support and sustain such learning.

2. Theoretical Framework

2.1. Lesson Study as a Professional Learning Practice

Lesson Study is widely characterized as a form of collaborative professional learning in which teachers, as a research team, set the goal, plan a research lesson proposal, observe the research lesson, discuss with a shared research focus, and summarize learning for their next step. Rather than a classroom observation with colleagues as an occasional event, Lesson Study constitutes a series of research done by teachers as professionals, which comprises teacher-driven inquiry, collective examination of teaching and learning, and the public sharing of practice to update the professional knowledge among the learning community. Through recurrent engagement in these practices, teachers develop their understanding of the lesson as an object of inquiry. This study adopts this view of Lesson Study as a professional learning practice and examines how teachers come to understand Lesson Study as a coherent set of professional learning practices.

To investigate how participation in LSIP-JR may influence teachers’ learning, this study draws on the theoretical model of Lesson Study developed by Lewis (Lewis, 2016; Lewis et al., 2019). Their model conceptualizes Lesson Study as a professional learning environment that integrates multiple theoretical perspectives, including Knowledge Integration Environments, Self-Determination Theory, Self-Efficacy Theory, and Pedagogies of Practice. Based on this theoretical model, participation in the process of Lesson Study is expected to influence four dimensions, teachers’ knowledge, beliefs, professional learning routines, and norms, as well as their ways of engaging with curriculum and instructional tools. These pathways may, in turn, contribute to improvements in student learning, while student learning outcomes can also affect teachers’ knowledge, beliefs, professional learning routines, and curricula. This study focuses on how teachers develop an understanding of Lesson Study as a form of professional learning practice through participation in LSIP-JR, drawing on this theoretical model to guide the analysis.

2.2. Pathways of Professional Learning in Lesson Study

Theoretical model of Lesson Study (Lewis, 2016) conceptualizes Lesson Study as a professional learning practice that functions through multiple interrelated pathways. Participation in Lesson Study has been suggested to influence teacher knowledge, teacher beliefs and dispositions, teacher learning community norms and routines (e.g., expectation of improvement, collegial observation, collective responsibility) and curriculum (e.g., mathematical tasks, instructional sequence). In other words, these four dimensions function as intermediates between the entire practice of the Lesson Study cycle and students’ outcomes, which would vary students’ outcomes. From this theoretical perspective, this study focuses on two aspects where empirical research is relatively limited: teachers’ understanding of the norms that structure professional learning communities in Lesson Study and teachers’ conceptualization of curriculum materials, instructional tasks, and instructional sequences as objects of inquiry.

These aspects are theorized as core mechanisms through which Lesson Study supports sustained professional learning and, ultimately, student learning. In the context of LSIP-JR, these pathways may become particularly evident as participants are positioned to observe and reflect on key processes of Lesson Study in a coherent and recurrent way, which allows them to compare and reflect on professional practices that differ from their prior experiences.

To examine how participants come to reconceptualize curriculum materials, instructional tasks, and instructional sequences as objects of inquiry (RQ3), this study draws on Cohen and Ball’s (1999) conceptualization of curriculum as a central site for teacher learning. This perspective provides a theoretical basis for analyzing how participants come to perceive curriculum materials and instructional sequences not merely as resources to be implemented but as objects of collective inquiry and professional learning, directly informing the analysis of RQ3.

2.3. Lesson Study as Teacher-Driven Research: Analytical Lens

This study adopts Lesson Study as teacher-driven research as an analytical lens to examine how participants interpreted their experiences in LSIP-JR. In the Japanese context, Lesson Study has historically functioned not only as a place of professional learning but also as a place of research, where teachers systematically investigate to improve their classroom teaching and learning (Fujii, 2016; Takahashi & McDougal, 2016; Takahashi et al., 2022; Takahashi & Wake, 2023). Findings that emerged through the Lesson Study are consolidated among the research communities and disseminated as school or district research reports (Kenkyuu Kiyou) or professional publications. In some cases, this informs curriculum materials, such as textbook problems in mathematics, and national-level discussions for future curriculum reform (e.g., Shimizu, 2019). These practices define the lesson as an interaction among students, teachers, and curriculum content, thereby positioning it as an object of inquiry. It is for this reason that the specific lesson to be examined in the process of Lesson Study is referred to as a Research Lesson.

LSIP-JR was not designed to transmit the Japanese model of Lesson Study as content to be learned. Rather, the program enabled participants to observe the research process of Lesson Study and its objects of inquiry from a third-party perspective. Participants were thus positioned to critically examine the entire process of Lesson Study in Japan, deciding what to notice, how to interpret observed practices, and what to articulate as their own learning. Adopting Lesson Study as teacher-driven research as an analytical lens, therefore, guides the analysis of participants’ written reflections, illuminating how they came to understand the nature of Lesson Study through observation and interpretation.

3. Methodology

3.1. About LSIP-JR Participants

This study examines the professional learning of international educators who participated in LSIP-JR in 2023 and 2024. In these two years, a total of five LSIP-JR sessions were conducted in Tokyo and Yamanashi, organized by IMPULS at Tokyo Gakugei University.

Participation in LSIP-JR was based on an open international call for applications, announced approximately six months prior to each session. Program information was disseminated globally through U.S.-based non-profit organizations supporting teacher education, teacher educators who lead Lesson Study initiatives in various regions or countries, and professional networks related to Lesson Study. In cases where institutional funding was provided, participants were presumed to have been selected through their institutional PD annual plan and approval processes. Applicants completed an application form that included their current role, the name of the person who supports the application, prior experience with Lesson Study, and the expectation to learn from the program. Based on this information, participants were selected for each LSIP-JR session.

Across the five sessions, a total of 120 participants were accepted. Approximately 92% were educators based in the United States. The other participants were based in Cambodia, Denmark, Ireland, Israel, and the United Kingdom. Participants were classroom teachers, school administrators, university faculty, and instructional coaches. Their prior experience with Lesson Study varied widely, from teachers who had already been involved in the Lesson Study for several years to educators with limited or no prior direct experience but a strong interest in the approach.

Learning in LSIP-JR is fundamentally dialogical, based on shared observations among participants with diverse backgrounds and experience levels. Considering the sample size and research design, this study does not examine subgroup differences. Instead, it focuses on how participants interpreted their own immersive experiences and articulated new understandings of Lesson Study as a professional learning practice.

3.2. Data

This study examines participants’ reflective journals produced as a part of the post-program requirements. Aligned with the theoretical framework, the reflective journals are treated as artifacts of participants’ interpretations and conceptualizations, articulated expressions of their professional learning experiences. Reflective journals were collected from 54 participants across the program years under study (submission rate: 45%). Participants were instructed to complete reflective journals about mathematics teaching and learning in Japan and the Japanese Lesson Study within one month after returning home, summarizing their learning from the program.

The following prompt was provided to all participants:

“Please write a reflective journal about mathematics teaching and learning in Japan and the Japanese Lesson Study, due by July 31, 20xx, for possible inclusion in our newsletter and on the IMPULS website.”

Importantly, the timing of data collection situates the journals at a reflective distance from the immediate participating program context. Participants were encouraged to draw on daily reflections accumulated during the program while also reassessing their experiences retrospectively. As a result, the journals frequently include metacognitive commentary on their perspectives contrasted with their prior understanding. These reflective accounts provide insight into how participants came to interpret Lesson Study as a professional learning practice, which is central to RQ 2 and RQ 3.

To better understand the background of participants’ written reflections and to support the interpretation of meanings articulated in the reflective journals, this study examined daily reflections voluntarily submitted by individual participants during the program and lesson plans developed by Japanese teachers for the research lessons observed in Japan. These daily reflections and lesson plans were not treated as a primary data source but were used as complementary resources to contextualize participants’ written reflections and to inform the researchers’ interpretive analysis of the reflective journals.

3.3. Analytical Approach

The data were analyzed using qualitative thematic coding (Flick, 2009/2011) to identify patterns of professional learning. Grounded in constructivist and social representation theory, Flick’s approach treats reflections not merely as individual accounts but as socially constructed meanings shaped among participants.

The analysis proceeded in the following stages. We conducted thematic coding and document-based qualitative analysis using Taguette, an open-source, web-based qualitative analysis tool. All textual data were imported into Taguette as separate documents and organized by participants. Initial coding was performed to identify salient ideas and incidents related to teachers’ professional knowledge or assumptions.

The reflective journals were first divided into meaningful segments of approximately 100 words each. Segmentation was conducted by the researchers prior to thematic coding and was guided by shifts in topic or focus within each reflection; the 100-word length served as a flexible guideline rather than a fixed unit to preserve the coherence of meaning within each segment. The average number of segments in one journal was 14.7. Next, each segment was tagged with two categories: the subject of reflection—“Lesson Study”, “Teaching & Learning”, or ‘Other’—and the reflection process, which includes “prior”, “during”, or “future”. These temporal labels were used to indicate how participants positioned their reflections in relation to prior understanding or past experience before participating in LSIP-JR, specific events during LSIP-JR, or future practice or mindsets after participating in LSIP-JR. And these were not treated as evidence of transformation in participants’ individual perspectives. Furthermore, for segments tagged with “Lesson Study” or “Teaching & Learning,” thematic coding was performed. The coding scheme was developed through an iterative process that combined concepts from the theoretical model of the Lesson Study (Lewis, 2016; Lewis et al., 2019) and elements of the Lesson Study process (Fujii, 2016; Takahashi & McDougal, 2016; Takahashi & Wake, 2023) with inductive refinement based on repeated reading of the data sets. Pilot coding was conducted, and the codebook was revised accordingly. In the end, 10 subcodes were assigned for “Lesson Study” and 14 for “Teaching & Learning.”

Every segment is assigned to one of the major codes: “Lesson Study”, “Teaching & Learning”, or “Other”. For segments coded “Lesson Study” or “Teaching & Learning”, subcodes are assigned to those containing specific descriptions. Segments describing only general aspects of “Lesson Study” or “Teaching & Learning” (e.g., “It was good to see LS in Japan in practice”) have only one major code and no subcode. For example, if a participant wrote that “I valued the way Japanese lesson plans focused on student learning by recording the anticipated answers of students”, this was coded as a mention of both planning, focus on student learning, and anticipated students’ responses (Matsuda & Lewis, 2016). Respondents mentioned Lesson Study in a total of 374 segments, which were subsequently grouped into 10 categories.

Coding procedures were carried out by two independent coders. The lead author conducted the initial coding, which was subsequently reviewed by the second author. Disagreements occurred primarily in the application of subcodes and prompted discussion and refinement of code definition by using a shared codebook.

4. Findings

4.1. Overview of Coded Description

In Table 1, we summarize the results of the initial coding frequency. Table 2 and Table 3 show sub-code frequencies for “Lesson Study” and “Teaching & Learning”.

Table 1. Initial Code Frequency.

	2023s1	2023s2	2023s3	2024s1	2024s2
Lesson Study	112	44	67	64	87
Teaching & Learning	147	33	46	88	58
Other	34	12	12	32	16

Table 2. Sub Code Frequency of the Code “Lesson Study”.

	Total Number of Segments	Number of People (n = 54)	Response Rate (%)	Coding Rationale
L01_Purpose	33	21	38.9	Describe purpose, significance, or reason for LS.
L02_Research Theme	17	12	22.2	Describe the research theme for the specific school visited or as a key role for LS.
L03_Lesson Plan	37	21	38.9	Describe the Lesson Plan for the research lesson, its contents, its details and its use.
L04_Observation	39	18	33.3	Describe research lesson observation, how to observe, what to observe.
L05_PLD	51	34	63.0	Describe Post-lesson discussion, what are discussed, focused and how to organize.
L06_Koshi	28	17	31.5	Describe Koshi; knowledgeable others, final commentator, who delivered the final comments, contents of the comments and its role.
L07_School-wide	28	19	35.2	Describe school-wide lesson study or about participation of all teachers in a school.
L08_Teamwork&collaboration	77	36	66.7	Describe team work, collaboration among participating teachers including school administrators for LS
L09_Professional	39	29	53.7	Describe professionalism, teachers profession, professionalization.
L10_Teachers’ ownership	17	13	24.1	Describe teachers’ ownership, willingness or motivation for LS.

Table 3. Sub Code Frequency of the Code “Teaching & Learning”.

	Total Number of Segments	Number of People (n = 54)	Response Rate (%)	Coding Rationale
T01_Learning Progression& Connection	52	27	50.0	Describe the learning progression in the lesson plan, textbook, curriculum OR describe students’ learning progression; the pathway to construct their knowledge, how to relate their learning with prior and future learning.
T02_Math task & contents	29	19	35.2	Describe the mathematics task or problem of the day OR teaching contents, how to select the number, situation, setting the difficulty.
T03_Multiple Solution & Idea	12	8	14.8	Describe the observation of students’ multiple solutions, ideas, or ways of thinking.
T04_Questioning&feedback	27	21	38.9	Describe the teacher’s questioning, prompt, feedback during the lesson taught.
T05_Collaboration&Participation	48	26	48.1	Describe the collaboration, participation, and contribution among students in the lesson.
T06_Independent	18	17	31.5	Describe the observation during the period of independent problem-solving, and how individual ideas and solutions are used in whole-class discussion OR students’ independence without peer support to tackle the task.
T07_Discussion	40	21	38.9	Describe classroom discussion, nature of discussion among students.
T08_Notebook	20	14	25.9	Describe students’ note-taking and its contents and usage.
T09_Routine&technique	19	15	27.8	Describe the classroom routine work, teachers’ techniques to motivate students or develop fluency, which seems to have regularly appeared in the classroom.
T10_Productive struggle	20	14	25.9	Describe students struggling, showing persistence to tackle the task, which provides a chance for learners to deepen their conceptual understanding
T11_Observe students work	35	26	48.1	Describe what and how teachers observe during the lesson in general, during whole class discussion or individual solutions/idea
T12_Anticipate solution	14	13	24.1	Describe students’ anticipated response written in the lesson plan or reasons why teachers need to anticipate
T13_Boardwork	14	10	18.5	Describe board writing, its contents, and its role.
T14_Explain & Listen	10	7	13.0	Describe students’ explanations OR how they listen to each other.

The results of the analysis revealed that learning related to Lesson Study was drawn out as the 10 themes shown in Table 2. Upon examining these coded descriptions, their described learning in Lesson Study was organized into three categories: specifically, “purpose of Lesson Study,” “process of Lesson Study,” and “the organizational and cultural foundations supporting Lesson Study”. Descriptions coded and grouped as “purpose of Lesson Study” and “process of Lesson Study” can be addressed as evidence for investigating RQ1. Also, descriptions coded and grouped as “the organizational and cultural foundations supporting Lesson Study” correspond to Lewis’s (2016) pathway to Lesson Study outcomes: teacher learning community norms and routines (e.g., expectation of improvement, collegial observation, collective responsibility). Examining these relevant descriptions can result in a response to RQ2.

In the same way, learning related to teaching and learning is drawn out in terms of the 14 themes shown in Table 3. These 14 themes can all be considered teacher knowledge of content, student thinking, curriculum, and pedagogy, as reported by participants as what they learned during LSIP-JR. In this study, we examine teachers’ conceptualization of curriculum as a pathway to the outcomes of Lesson Study, informed by Lewis’s (2016) Theoretical Model of Lesson Study. Therefore, we focus on “T01_Learning Progression & Connection” and “T02_Math task & contents”, and how these are understood as subjects for Lesson Study as research, which responds to RQ3.

4.2. How Do Participants Come to Understand Lesson Study as a Form of ProfessionalLearning Practice Through Participation in LSIP-JR?(RQ1)

4.2.1. Purpose of Lesson Study

Participants’ reflective journals clearly articulated the purpose of Lesson Study in their own words, demonstrating a deliberate effort to verbalize what Lesson Study is and its intended purpose. Throughout the data, participants described Lesson Study as a means to become a better teacher, a practice supporting professional growth, and a framework for developing student-centered teaching practices. They also described Lesson Study as research conducted by teachers themselves. Multiple participants described it as e.g., “a framework that allows teachers to think and study so that they become experts themselves in the content they present” [2023s3:AO], and emphasized that “the true intent is not to showcase a teacher’s talent in the classroom, but to really learn from the observational experience” [2024s1:FU].

A noteworthy finding is that participants understood doing Lesson Study not as the primary objective but as a learning process situated within broader school-based research. A participant serving as a regional instructional leader described Lesson Study as a learning process that begins with teachers’ “questions,” highlighting the importance of a shared school research theme that teachers think about and want to explore.

“In attending this round of IMPULS, I had a few important takeaways. First, it became more clear to me the importance of utilizing Lesson Study as a learning process in the pursuit of studying a particular question versus seeing Lesson Study as the end unto itself[sic]. This highlights the need for a school research theme that a faculty is eager to explore.”

[2024s2:KL]

This perspective supports the understanding of Lesson Study not as an isolated activity or a practice focused on presenting outcomes but as a means to support continuous inquiry. Thus, understanding Lesson Study from the dual perspectives of professional development and research aligns with the widely shared definitions and purposes of Lesson Study in prior research. Therefore, it is reasonable to infer that many participants possessed a certain general understanding of the purpose of Lesson Study even before joining LSIP-JR.

However, it is noteworthy that participants’ explanations extended beyond such general, normative understandings. As the following excerpts indicate, Lesson Study was also understood as a place for teachers to intentionally challenge themselves through research and accepting risks. Some participants described how Japanese teachers utilize Lesson Study as a “platform” for addressing challenging mathematical content—such as division of fractions—that is difficult for both teachers and students, describing it as follows:

“This insight has reinforced my understanding that lesson study is not solely about showcasing exemplary teaching practices; rather, it is a means of collectively developing innovative tools and methodologies to effectively teach challenging topics, thus optimizing student learning outcomes. This principle will serve as a guiding message in my research endeavors.”

[2023s1:DC]

“One aspect I really valued about lesson study is that teachers choose a topic based on an area that students are having difficulty finding success. The mindset seems to be that if you want the data to change you have to teach in a different way than you have in the past. By constructing empirical observations of teaching and learning, hypotheses can be made about the effects of teaching on student learning. Improvements in teaching can be made using analysis of findings, thus, keeping the focus on student learning.”

[2023s1: HH]

Another participant described Lesson Study not as an activity premised on evaluation or competition but as a practice where teachers can carry out inquiries driven by their own interests while also carrying responsibility for their choices. This description reveals an image of Lesson Study as an activity where a sense of safety and tension both coexist.

“I was worried about myself, but that was and is a response to the judgment and competitive culture found in the American education system. There is space in the lesson Study ideology to take risks with topics that we want to learn more about.”

[2023s3:AO]

A recurring theme in these descriptions is the understanding purpose of lesson study: it is recognized not merely as a means to improve lessons by fixing “what didn’t work,” but as a proactive, dynamic practice enabling the exploration of new ideas, confronting challenging tasks, and facilitating collective inquiry.

4.2.2. Process of Lesson Study

When the elements that emerged through thematic coding were compared with the process of Lesson Study (Fujii, 2016), it became clear that the participants’ learning encompassed four of these components: “Research Theme (L02)”, “Lesson Plan (L03)”, “Observation(L04)”, and “PLD(L05)”. These encompass all four elements (Study, Plan, Teach, Reflect) that compose the cycle of Lesson Study in the theoretical model of the Lesson Study (Lewis, 2016; Lewis et al., 2019).

Research Theme

Regarding setting the “Research Theme (L02),” some participants described recalling specific research themes, e.g., “Nurturing students to expand their own ideas and express themselves” and “Nurturing children who can think about and deepen their learning collaboratively aiming for students who can keep learning while self-regulating themselves”. These are the research themes of particular schools observed in Japan, typically spanning multiple years and multiple research lessons and written in the research lesson proposal.

“A cornerstone of Japanese Lesson Study is the identification of a research theme. This theme serves as a guiding principle, balancing specificity and generality to ensure it resonates across various lessons and grade levels. Themes are grounded in observable challenges in student learning and teacher practices, such as fostering logical reasoning or enhancing collaborative problem-solving”.

[2024s2:EJ]

Furthermore, participants’ descriptions of their reflections emphasize the importance of setting a common research theme or research question. As described below, it has come to be understood that sharing a research theme within the school or in the local research community from the initial stage of its setting promotes motivation for the Lesson Study itself, ensures consistency in the hypothesis verification process, and fosters professional growth as a whole team.

“I think a common research theme and perhaps a common research question would help us learn together and from one another in our district… In the past, the research themes and questions felt like just words to me when I participated in lesson study. Now I have a stronger sense that lesson study can be driven by real curiosity, or even driven by some frustration or pain point we are experiencing in our work with students.”

[2023s1:GC]

From the perspective of school leadership, the importance of a shared research theme was also articulated as a condition for aligning teachers’ work across multiple dimensions of classroom practice, which is not limited to the specific research lesson.

“One thing I continue to wonder about is how sites build consensus around a school research theme… I am thinking about because it allows a school to be on the same page with how they are approaching curriculum, lesson planning, collaboration and reflection. When everyone is working toward a common goal it helps teachers and students become more aligned and ultimately gain success.”

[2024s1:AN]

Taken together, these accounts indicate that participants understood the research theme as a shared analytical lens that structures inquiry throughout the Lesson Study process. This participant further described how a shared research theme functions as a common frame of reference that disciplines professional dialog and participation.

“Another example is all participants, even those who are not teachers like nurses, made sure to ground themselves in the research theme and made all feedback related to that topic and that topic only.”

[2024s1:AJ]

These descriptions suggest that some participants came to recognize research themes as the central guiding principle of Lesson Study. This indicates they understand Lesson Study not merely as a collaborative activity but as a research-oriented professional practice that teachers systematically investigate.

Lesson Plan

Regarding “Lesson Plan (L03)”, many participants described the level of detail and meticulousness found in Japanese lesson plans, including information about students’ prior learning and anticipated student responses. Even though they did not have a chance to observe the actual planning stage, they had access to read lesson plans translated into English.

“This process highlighted the meticulous nature of Japanese Lesson Study. It is not about creating a perfect lesson but about deeply understanding the teaching and learning process. The deliberate planning showed how much thought goes into ensuring lessons are meaningful and effective.”

[2024s2:PT]

Participants’ reflections also described how they understood the negative aspect of Lesson Study as an appreciation of its necessity for the Lesson Study as research. For example, as the following participant’s description indicates, it is evident that they are using their prior knowledge of the lesson plan to understand the actual practice of lesson planning in Japan as articulated in the lesson plan.

“I appreciated the opportunity to read the lesson plans before each lesson study. They gave insight on what the lesson would be about and the team’s rationale for each decision made. I was very impressed that each step of the lesson was so well thought out and that there was a reason for each aspect of the lesson. When I was doing lesson study in the 23–24 school year, I didn’t understand the rationale behind writing a lesson plan…why would we need to write a long report on our work? Having seen multiple lesson plans from Japan, I now understand that it’s necessary in order for the team to thoroughly think through all of the aspects of the lesson.”

[2024s1:FU]

“While it may seem counter-productive to have to redo, review, and rewrite portions of the research lesson plan proposal as new ideas arise, this ultimately helps create a more well thought out lesson plan that will guide participants’ observations on the day of the lesson and improve their understanding of teaching and student learning.”

[2024s2:KL]

These descriptions emphasized collaboration as a team to develop a lesson plan from the planning stage, because this can foster shared perspectives during observation and provide observers with a common observation framework. Some descriptions also revealed that participants critically reflected on existing knowledge, such as the notion that lesson plans in Lesson Study must be perfect model plans or that lessons must be conducted exactly as outlined in the lesson plan.

Observation

In Lesson Study, learning does not occur solely through conducting a research lesson as the instructor or a member of the research team. In fact, teachers in Japan have more opportunities to learn by observing research lessons than conducting research lessons. Therefore, it is meaningful to clarify what participants learned through LSIP-JR about the professional practice of observing research lessons, because this process is common to all teachers and is the one they experience most frequently. In LSIP-JR, each group had the opportunity to observe four to five live mathematics research lessons. An analysis of participants’ written reflections coded “Observation (L04)” revealed that participants noted the focus of observation, emphasizing the need to focus on students’ learning, e.g., “This shift from teacher-centered to student-centered observation provides rich data for post-lesson discussions” [2024s2:EJ].

Beyond a general understanding of observing students’ learning, some participants articulated a more structured understanding of observation as a professional, research-oriented practice. Their reflections indicate that research lesson observation is not an intuitive or spontaneous activity, but one that requires shared understanding of the research theme, intended lesson objective, its design, and its hypotheses. In this sense, participants described the practice of research lesson observation as a form of data collection that enables meaningful post-lesson discussion to verify the hypothesis.

“It was helpful to hear about the observational structure (understand the goal, non evaluative observation, create a hypothesis, provide feedback)… It is important that all individuals involved in collaborative lesson research have this similar understanding of what an observation is. Understanding the lesson design and goals of the lesson is important to frame the observation…Feedback is impactful when those observing have done the work of informing themselves of the research, understand the goals and have collected careful data.”

[2023s3:LG]

This description suggests that the practice of observing research lessons was understood not as a venue for evaluating teachers’ instruction but as a process for systematically generating data related to shared research questions.

Post-Lesson Discussion (PLD)

Among the processes of Lesson Study described by LSIP-JR participants, “PLD (L05)” was the most frequently mentioned, appearing in 63% of the responses. Participants emphasized the importance of focusing discussions on students’ learning processes rather than on teachers’ actions and highlighted the need to cultivate a culture of sincere reflection, mutual respect, and openness to diverse perspectives. They also reflected the value of constructive, collaborative dialog aimed at developing shared understanding, as well as conducting discussions across grade levels and professional roles to promote school-wide inquiry. Furthermore, participants emphasized the importance of discussion of the relationship between subject content and clearly defined learning objectives.

For example, this participant described PLD not as a practice for evaluation or advice but as a practice for jointly analyzing observed data. Moreover, the participant recognizes the moderator’s role in creating such a place to construct collective understanding.

“The post-lesson discussion, moderated skillfully, is a critical component of the process. Feedback begins with an acknowledgment of the teacher’s effort, fostering a culture of respect and collegiality. Discussions are not about evaluating the success of the lesson but about analyzing student learning and identifying areas for improvement. This reflective practice ensures that lessons continue to evolve, guided by collective insights.”

[2023s3:EJ]

Another participant emphasized that PLD functions as a mutual learning process. In this process, both giving and receiving feedback are experienced as opportunities for professional growth. It is not a relationship of “receiving/giving” feedback, but rather, everyone is considered a “learner.”

“Seeing teachers think critically about what they observed during the various research lessons’ debriefs was enlightening. The system has created teachers who really want constructive feedback, because they see it as an opportunity for growth and teachers who are comfortable giving that feedback because it benefits all. Basically, the first reason is simple because participants know it is a win, win situation.”

[2023s3:CJ]

4.3. How Does Participation in LSIP-JR Influence Participants’ Perceptions of the Norms of the Learning Community of Lesson Study? (RQ2)

Within the five codes categorized under “the organizational and cultural foundations supporting Lesson Study,” this paper focuses on “L10_Teachers’ ownership.” This focus corresponds most directly to the teacher learning community norms and routines articulated in Lewis’s (2016) theoretical model, providing a consistent lens to discuss how Lesson Study, as research-oriented professional practice, can be sustained. Learning community norms and routines are not externally imposed constructs but socially constructed through interactions within the community. In other words, they are the principles of action that community members take for granted. In Lesson Study as a professional learning practice, teacher ownership is one of the most prominent manifestations of such norms. Therefore, participants’ recognition of ownership as a defining characteristic of Lesson Study itself can be understood as an effect of participating in LSIP-JR. Therefore, this study focuses its analysis on “L10_Teachers’ Ownership” to examine how participants recognize the norms of the Lesson Study learning community.

Teachers’ Ownership

Participants described that Lesson Study in Japan is fundamentally characterized by teacher autonomy, which appears as professional choice, risk, and shared responsibility within a structured framework. These reflections highlighted participants’ understanding that Lesson Study operates as a teacher-driven process grounded in professional choice and autonomy. Throughout the entire Lesson Study cycle, participants explained that “ownership” is carried out through multiple opportunities for teachers to participate in, shape, and sustain collaborative inquiry. For example, at the stage of setting the research theme, some participants emphasized that ownership is expressed through teachers’ willingness or curiosity to identify questions that involve uncertainty and challenge, rather than selecting topics that ensure smooth or successful lessons.

“Which brings me to the point made during IMPULS made on Day 1 that “research lessons should be new ideas we want to study and explore”…There is space in the lesson Study ideology to take risks with topics that we want to learn more about…When we choose to step into our zones of discomfort is when the greatest changes occur and we evolve into the next area of risk.”

[2023s2:AO]

“A key revelation from observing Japanese Lesson Study is that it starts with questions, not answers. The process prioritizes curiosity and a willingness to explore over showcasing expertise.”

[2024s2:EJ]

These descriptions suggest that participants came to understand ownership at this initial stage of Lesson Study as the right and responsibility of the teacher to define the subject of inquiry themselves. Ownership can be identified in the planning stage of Lesson Study, particularly through collaborative lesson preparation. Participants noted that collaboratively developing a research lesson proposal created an opportunity for all teachers to meaningfully engage in student learning investigations, regardless of who actually taught the research lesson.

“The shared lesson preparation helped everyone to be invested in the student learning process and allowed them to share ownership of the lesson. What an amazing model for growth!”

[2023s1:SK]

Although participants did not observe the actual process of discussion to develop the research lesson proposal in Japan, they noted that lesson plans were developed by the team. The fact that lesson plans as research proposals are developed under the ownership and responsibility of the team of teachers was evident from the observation that, during LSIP-JR, the research team representative explained the research proposal in all PLDs observed.

By observing PLDs, participants also noticed ownership as closely linked to norms of vulnerability and learning from practice. Rather than viewing the research lesson as a performance to be evaluated, teachers were observed to openly share moments of uncertainty and invite feedback on their instructional decision-making. One participant described these moments as transforming the research lesson into “a genuine group learning experience, rather than a performance,” and highlighted the professionalism involved in acknowledging struggle and learning from mistakes. Such reflections indicate that ownership within Lesson Study entails responsibility for making teachers’ decisions available for collective verification to ensure shared learning.

“I was inspired by some wonderful examples of teachers approaching the process with curiosity and openness. Teachers shared their moments of tricky decision making and invited feedback from colleagues. So much of teaching involves deciding in the moment which way to go, and it’s interesting to hear another teacher describe that process. In those moments I felt that the research lesson was a genuine group learning experience, rather than a performance. I hope that I will remember the vulnerability and professionalism of the Japanese teachers I observed, to guide my own practice. We often want to be seen as perfect and hide any uncertainty, but I think we learn more when we do our best but acknowledge that every lesson is an opportunity to learn from struggle and mistakes, for us as well as our students.”

[2023s1:GS]

This awareness of learning community norms that embrace vulnerability demonstrated by Japanese teachers is an insightful point. That is, ownership in Lesson Study was recognized not as placing responsibility on individual teachers, but as creating a shared place where teachers collectively experience the autonomy to explore, acknowledge difficulties, and learn from any lesson. Observing the everyday, honest professional practices of Japanese teachers appears to have deepened participants’ understanding of the collective responsibility norm inherent in the Lesson Study process.

Participants also associated teacher ownership with a shared understanding of Lesson Study protocols and a corresponding sense of individual responsibility for professional contributions. One participant observed that in Japanese Lesson Study, “everyone was involved and aware of the lesson study protocols, and that everyone was responsible for their own input [2024s1:SD]”, noting strong buy-in not only from teachers but also from staff and administrators. This reflection highlights that ownership is enacted through disciplined participation. In other words, teachers are expected to understand the purposes and procedures of Lesson Study to contribute thoughtfully and responsibly at each process.

Importantly, this sense of responsibility was grounded in the view of teachers as independent yet interdependent learners. As another participant reflected, teachers are expected not to simply follow established patterns or traditions but to challenge themselves to grow professionally and to learn from one another, recognizing that “we all have ideas that can help each other learn and grow as educators [2024s1:SP]”. Such descriptions suggest that Lesson Study is understood as a professional practice in which each teacher is acknowledged as a legitimate contributor to inquiry rather than as a passive recipient of expertise. Ownership, in this sense, is sustained by a norm that treats all participants as capable of generating insights from practice and responsible for advancing collective learning.

These reflections demonstrate that participants came to recognize teacher ownership as a defining norm of Lesson Study learning community. It is enacted consistently across all phases of the process. Ownership was understood not as unrestricted autonomy but as agency exercised within a shared framework of inquiry, mutual responsibility, and respect for professional expertise. The fact that participants were able to articulate these norms explicitly suggests that LSIP-JR influenced how they perceive the organizational and cultural foundations that sustain Lesson Study as a research-oriented form of professional practice.

Moreover, one participant described that teacher autonomy in Lesson Study does not imply unrestricted freedom or disorder in lesson planning. Rather, teachers’ discretionary decisions are exercised within a structured framework aligned with national curriculum standards and the educational policies or goals of the school or district.

“I identified the critical role of teachers in curriculum design. Unlike standardized approaches that dictate teaching practices, LS grants teachers autonomy over the “how” of teaching, recognizing their expertise and valuing their professional identity. It does not mean anarchy in teaching practices. While teachers and schools are provided with a curriculum designed by state-level committees in education, they are also granted the autonomy to adapt/enact those curricular guidelines and rely on their own expertise and LS team expertise to provide high-quality math instruction.”

[2024s2:DG]

As this participant described, it was highlighted that teachers’ ownership in Lesson Study is grounded not in individual preference but in collective responsibility for investigating and enacting curriculum through research-oriented practice.

4.4. How Does Participation in LSIP-JR Influence Participants’ Perceptions of the Curriculum Materials, Instructional Tasks, or Instructional Sequences as Objects of Inquiry? (RQ3)

To address RQ 3, this section examines participants’ descriptions coded under two themes identified among the 14 analytic categories: “T01_Learning Progression & Connection” and “T02_Math Task & Contents.” By analyzing these descriptions, we clarify how LSIP-JR participants understood teaching materials, instructional tasks, and the sequences as subjects for inquiry in Lesson Study.

Descriptions coded as “T01_Learning Progression & Connection” indicate that participants paid particular attention to the detailed description of learning sequences written in Japanese lesson plans. Several participants noted that lesson plans often included extensive descriptions of unit structures and learning progressions across grade levels. These observations reflect participants’ understanding that one research lesson is not designed as an isolated lesson. Rather, the research lesson is usually embedded within ongoing instructional sequences in the unit. Therefore, meaningful analysis of the research lesson requires simultaneous consideration of the goals of the unit, students’ prior learning, and subsequent lessons.

Some participants described a lesson plan that visualized mathematical concept development from the first through sixth grade, highlighting the strength of vertical learning progression within a school. For example, this participant emphasized that Japanese teachers actively investigated how specific mathematical concepts function within learning progressions across grades and units, using evidence from students’ prior learning.

“Teachers used the knowledge they had of individual mathematical concepts and researched how those concepts live within mathematical progressions over the grades. Teachers also leveraged previous learning of students through lessons in the unit and through the written reflections of students that was [sic] noted in each of their research lessons. The cycle continuously stemming from student learning to drive research, planning, and understanding that is not only meant for students but teachers as well.”

[2023s2:AO]

While many descriptions coded as “T02_Math Task & Contents” primarily documented the types of mathematical tasks used in the research lessons, one participant emphasized the importance of teachers solving the mathematical problems themselves prior to the research lesson.

This description suggests participants’ understanding that mathematical tasks were no longer viewed simply as instructional materials to be carried out but as objects of inquiry that require careful examination, hypothesis generation, and contextual understanding.

“One of the greatest things that I’ve learned is that teachers have to do the math first in order to anticipate what is going to happen. When the pre-lesson discussion involved us doing to [sic] the math and trying it out on our own, it was easier to digest the lesson plan as a whole and see what we’re[sic] the possible outcomes that the students would come up with.”

[2023s2:TY]

This understanding can be attributed to the design of the LSIP-JR program, in which facilitators consistently allocated time before research lesson observations for participants to work through the tasks themselves, consider multiple anticipated student responses, and situate the lesson within the Japanese textbook sequence and curriculum. Engaging in this process enabled participants to recognize that doing the mathematics in advance supports not only deeper content knowledge but also the formulation of hypotheses about how particular tasks might elicit specific forms of student thinking. It is an essential feature of Lesson Study as research, where lessons are interpreted as an interaction between teacher and students mediated by curriculum content.

4.5. Summary of Findings

Based on Lewis’s (2016) theoretical framework for understanding the impact pathways of Lesson Study, this study examined how participation in LSIP-JR influenced participants’ understanding of Lesson Study as a form of professional development.

Regarding RQ1, participants described their understanding of Lesson Study as a form of teacher-driven research. Participants emphasized the centrality of a shared research theme that will be found across the Lesson Study cycle. These descriptions suggest that participation in LSIP-JR supported participants’ recognition of Lesson Study as a systematic inquiry process embedded in teachers’ everyday practice rather than as an isolated or demonstrative event.

Regarding RQ2, participants’ descriptions illuminated how Lesson Study is sustained through socially constructed norms and routines within a learning community. Participants clearly recognized teachers’ ownership as they described voluntary participation, shared responsibility, and norms of vulnerability and learning from practice as a foundation for collective inquiry.

Regarding RQ3, participants described curriculum materials, instructional tasks, and learning progressions as objects of inquiry in Lesson Study. These descriptions suggest that participation in LSIP-JR influenced participants to understand the necessity of research on curriculum and instructional tasks.

In summary, participants came to understand Lesson Study through LSIP-JR as a place for research. This understanding was reinforced by the immersive experience of the entire process: sharing research themes, meticulous planning involving research on curriculum contents, observation focused on learning to collect various data, and collaborative reflection for validation. Lesson Study was recognized as an exploration involving challenges and risks and a place for collective learning, positioning it as a professional learning practice driven by teachers’ ownership.

5. Discussion

This discussion interprets the findings not with the aim of disseminating Japanese Lesson Study as a model to be replicated but to offer insights for teachers and educational leaders—both in Japan and internationally—who seek to make Lesson Study a more powerful, sustainable, and meaningful form of professional learning in their own contexts. Drawing on Lewis’s (2016) theoretical framework, this study focuses on two dimensions that have remained underexamined in prior research: teacher learning community norms and curriculum and instructional tasks as objects of inquiry. By analyzing how these dimensions became visible to international participants through their engagement in LSIP-JR, this discussion highlights conditions under which Lesson Study functions as a robust learning system rather than a procedural activity.

5.1. Norms Supporting Collective Inquiry Through Teacher Agency

This section discusses how participation in LSIP-JR enabled international participants to recognize the norms of teacher learning communities that sustain Lesson Study as collective inquiry. Building on Lewis’s (2016) framework, the analysis foregrounds teacher learning community norms, a dimension often not explicitly articulated in the Japanese context yet critical to the sustainability of Lesson Study, and examines how these norms are enacted and sustained through teachers’ collective agency.

Prior research has emphasized that Lesson Study in Japan is deeply embedded in the historical and cultural system as school-based professional practice (Fujii, 2014, 2016; Takahashi & McDougal, 2016). As a result, many of the norms that sustain it—such as shared responsibility for student learning, tolerance for uncertainty, and openness to critique—are pervasive but largely invisible and therefore rarely articulated by Japanese teachers themselves. This invisibility does indicates not their absence but rather their normalization within the professional culture.

The findings of this study suggest that these rarely articulated norms became visible precisely because they were encountered by participants positioned outside the Japanese educational context. International participants consistently interpreted research lessons not as polished performances designed to demonstrate best teaching but as provisional and uncertain inquiries into teaching and learning. Every unexpected student reaction and instructional uncertainty was understood not as personal failures to be silenced but as shared challenges to be jointly examined. This interpretation suggests a professional culture where vulnerability is openly acknowledged and responsibility for improvement is shared across the entire community rather than placed solely on individual teachers.

These observations strongly resonate with the “norms of teacher learning communities” identified by Lewis (2016), particularly those related to collective responsibility, psychological safety, and learning from practice. This research is distinctive in its approach to these norms, not from within Japan’s system but through an understanding illuminated by external participants’ reflection. It demonstrates how norms deeply embedded in daily practice—and thus difficult for insiders to articulate—can be reconstructed and analytically visualized through cross-cultural participation.

The norms of the teachers’ community are invisible and rarely reveal themselves unless observed by an outsider. Analysis of the descriptions provided by LSIP-JR participants revealed a key finding: the existence of a research theme is crucial. It is the research theme in Lesson Study that shapes these invisible norms and ties together each professional practice, steering collective inquiry in a certain direction. This means that the existence of a clearly articulated, shared research theme allows the norms of the teachers’ community to be shaped or transformed based on the direction of that theme. Lewis’s (2016) theory implies that when the norms of the teachers’ community change, student learning could also change.

5.2. Curriculum and Instructional Tasks as Objects of Inquiry Within Institutional Conditions

Building on the above discussion, this section turns to how curriculum contents and instructional tasks could be recognized as objects of inquiry through participation in LSIP-JR. In the Japanese context, Lesson Study is premised on the shared understanding that lessons, tasks, and materials are provisional and improvable, rather than fixed artifacts to be faithfully implemented. Such an understanding is sustained by learning community norms that value uncertainty, collective responsibility, and learning from practice. Within these normative conditions, teacher agency emerged not as individual autonomy detached from shared goals but as a collective capacity to pose questions, generate hypotheses, and try instructional ideas through developing a lesson plan as a proposal. Participants’ reflections suggest that agency in Lesson Study operates through teachers’ professional judgment about how tasks might elicit particular forms of student thinking and how instructional sequences might be refined in response.

Through carefully reading lesson plans and using them to interpret the lesson events, participants might be able to view curriculum materials and instructional tasks as objects for hypothesis generation and verification about student learning. When curriculum content becomes the subject of inquiry, it may require rethinking or revising one’s existing understanding of the content, students’ engagement and interaction with it, and the teacher’s role in mediating these interactions. In other words, it becomes possible to intentionally incorporate transformative teacher learning, as described by Mezirow (1991) and Cranton (1992), while respecting teachers’ autonomy. As a result, as Lewis (2016) shows, this may also affect teachers’ knowledge and beliefs about subject content. On the other hand, if the curriculum contents are not the subject of inquiry in a research lesson, even if teacher-student interactions are discussed during PLD, the cause of the specified problem may end up being treated as problems originating with the teacher or student.

Moreover, participants’ reflections indicate that the extent to which curriculum materials can be treated as objects of inquiry is mediated by institutional conditions in their home contexts. While Japanese Lesson Study operates within a system where such inquiry is culturally accepted and professionally expected, participants noted that in some educational systems, deviations from prescribed materials in the textbook may require structural support. This suggests that teacher agency in curriculum inquiry is not only normatively but also institutionally mediated and that sustaining Lesson Study beyond Japan requires attention to how these conditions interact.

6. Conclusions

This study discussed how international educators understand the nature of Lesson Study, specifically within the Japanese context. Lesson Study is teacher-driven research, and throughout the entire process, the professional practices that enabled inquiry were described in participants’ reflections. By analyzing these descriptions, this study clarified how the nature of Lesson Study is recognized and interpreted.

The results showed that conditions often treated as implicit within Japanese educational practice—such as the norms of the learning community and the perspective of understanding curriculum and teaching materials as objects of inquiry—become visible through the recognition of international educators. This visualization provides a frame of reference for re-examining Lesson Study as professional learning in contexts beyond Japan. Simultaneously, it offers a perspective that allows for the critical examination of Lesson Study practice itself within Japan.

This research does not present Lesson Study as a model to be followed. Rather, its aim is to clarify a conceptual framework for understanding how Lesson Study functions as a collective inquiry. These findings provide a foundation for teachers and professional development leaders who seek to conceptualize Lesson Study as a meaningful form of professional learning across diverse educational contexts.