This article describes the use of a lesson study approach to collaborative professional growth in an elementary science methods course. Preservice candidates designed and taught integrated science-mathematics lessons during the semester before their student teaching. Working in 8 teams of 3 student teachers, participants per team designed a common lesson and taught it in three different classrooms, critiquing and refining the lesson between each episode. Results support the use of lesson study to help preservice teachers develop a critical lens with which to view their practice. It encourages practitioners to take a reflective and engaged approach to teaching, focus on student success in their classrooms, take responsibility for classroom decision making, engage in collaborative practice, and participate as actors in the creation of the knowledge base for teaching. (Contains 1 figure and 2 tables.)