This chapter examines the theory of action in school reform for School as Learning Community at Kakioka Junior High School from 2005 to 2007, attending especially to the theory of action of Principal Yasunori Iwamoto. Kakioka Junior High School’s narrative teaching record chronicled the progress of school reform from 2005 to 2007. Further, Kakioka Junior High School’s school reform promoted lesson study reform by inviting Masaaki Sato as supervisor eight times over three years. Notably, Iwamoto pursued each teacher’s “self-transformation” in the lesson study reform, which could only be achieved by “organizational learning” or “double loop learning”, and he devoted himself to supporting that growth as a principal.