The present article addresses how lesson study can facilitate changing traditional norms of individualism, conservatism and presentism that constrain American teachers from learning from one another. The article investigates how lesson study can serve as a vehicle for developing teacher learning communities by developing or redeveloping teachers' professional identity to include continual improvement. While participating in a learning community, the norm becomes to innovate and inquire in order to learn how to better serve students. In a case-study mathematics department, teachers involved in lesson study embraced uncertainty; accepting that by researching lessons they did not know what would happen when the lesson was taught, and the process would better inform their future practice. Lesson study put student learning in the centre of the analysis and provided a structure for basing changes on teachers' professional intent to support students.