This article describes an innovative approach to developing preservice elementary science teachers' classroom confidence and skills. Based on lesson study approaches, preservice candidates designed and taught integrated science-mathematics lessons during the semester before their student teaching. Working in teams, candidates designed and taught a common lesson in 3 different classrooms, critiquing and refining their lesson between each teaching activity. Data collected from observations of classroom teaching events, team reports, and individual reflections were analyzed qualitatively. Results indicate that, over the 3 teaching events, there were dramatic improvements in lesson design and delivery, the management of the learning environment, the quality of students' engagements with meaningful content, and the quality of assessments and generation of student data.