While many teachers acknowledge that school-based lesson studies are useful for their professional development, those studies occasionally become routinized and fail to deliver diverse perspectives without promoting collegiality. This paper selects “Tojisha-kenkyu,” a community-based study of mutual help by those concerned with difficulties, as a type of practitioner research that may evolve school-based lesson studies into a new kind of research activity with distinct procedures and epistemology. School-based lesson studies inspired by “Tojisha-kenkyu” require changes in the conceptual understanding of causality, agency, practice, power, and teacher competency. The paper also discusses the feasibility of introducing such research into the current school education context in Japan.本研究はJSPS科研費JP16K04770の助成を受けたものです