Developing teacher expertise through the Change Laboratory in a Japanese elementary school

This study investigates how a Change Laboratory intervention fostered teachers’ professional learning and the emergence of new forms of expertise in a Japanese elementary school. Grounded in cultural-historical activity theory and its formative intervention methodology, it analyzes six Change Laboratory sessions conducted between September and December 2025 with the participation of all 23 teachers at the school. Through transcript-based chronological and contradiction analyses, the study traces how teachers’ learning expanded without following a linear developmental trajectory. The findings indicate a shift from improving individual lessons to transforming the school as a collective activity system. By using conceptual tools such as the triangular model of the activity system and the four-field model, teachers developed collaborative and transformative expertise through the collective redesign of the object, instruments, rules, community, and division of labor of the school’s activity system. These findings suggest that the Change Laboratory offers a powerful methodological framework and concrete methods to support teachers’ collaborative and transformative agency in whole-school educational changes.