This article describes the case of a Japanese junior high school that experienced a turn-around in three years from one of the worst schools to one of the best by utilizing lesson study for learning community (LSLC) as a managerial tool. It will focus on how the principal: (i) established a vision of reform, (ii) organized LSLC to involve the entire school and (iii) overcame problems in the process of implementing school reform based on LSLC. The principal placed top priority on making learning more collaborative and on including not only cognitive but also social and ethical aspects. He subsequently implemented LSLC beyond subject boundaries with special attention to joint observation of and reflection on lessons. Further, the principal interacted with the teachers individually and developed both collegiality among the teachers and the capacities of middle-level leaders.