Lesson study is a type of inquiry cycle used by educators seeking to improve instruction and student learning. Educator teams collaboratively study student thinking, design lessons, observe student learning during a live classroom lesson, and conduct data-driven analysis and reflection on evidence of success. The use of lesson study in the U.S. has been relatively rare, but the High Tech High Graduate School of Education has been supporting lesson study through its networks for school improvement for the last six years. In this article, the authors describe the theory and practice of how lesson study promotes self-efficacy, then show the results of a survey in which participating teachers overwhelmingly reported that participating in lesson study through that network supported their practice. The experience suggests that lesson study is a worthwhile investment, and action steps and tips for implementation in other schools are provided.