Background: In many Japanese junior high schools, class-based choral competitions are held as cultural events that foster musical understanding. These events involve not only music classes but also class activities. Each class performs in a concert hall or gymnasium, evaluated by teachers and other grade students. Despite diverse abilities and interests within public school classes, all students are required to participate. In this process, they generate and test rehearsal methods, overcome challenges, and extend individual ideas into collective practices. Such activities are expected to transform students’ meaning-making of learning and foster the development of agency.　Previous studies have focused mainly on the relationship between students’ motivation and learning outcomes, while the meaning-making of learning and the emergence of agency have remained underexplored. Engeström’s activity system offers a valuable framework to capture the transformation of learning communities and clarify the relationships and transitions among elements of the system.Purpose: This study aims to clarify how students’ perceptions of learning transform and how agency is generated by applying Engeström’s activity systems to a longitudinal analysis of choral learning across three years in junior high school.Method: Data consisted of students’ written reflections on choral learning in music classes during 3 years. To capture collective transformations across multiple classes, KH Coder (Higuchi, 2020), a text analysis software, was employed. The analysis focused on changes in characteristic and frequent words over time.Summary: The activity system showed transformations over time in five areas: (1) development of the subject, (2) deepening of tools, (3) expansion of the object, (4) structural changes in rules, community, and division of labor, and (5) qualitative transformation of outcomes. Students collaboratively created change by constructing activity systems through trial and error, engaging in cycles of expansive learning. Outcomes from one stage were carried forward into subsequent stages, indicating the development of agency.Conclusion: This study visualized the process of choral learning in Japanese junior high schools and demonstrated its connection to the OECD’s concept of fostering agency. While fostering agency is often presented as a new educational goal, this study suggests that its foundations have long existed within Japanese choral learning practices.