This study investigates the use of Lesson Study in three U.S. schools. Lesson Study is part of the culture of teaching in Japanese K-8 schools. Researchers in the United States brought the practice of Lesson Study ("jugyokenkyo" in Japanese) to light in the late 1990's while investigating reasons for differences in the performance of students from various countries on The International Mathematics and Science Study (TIMSS) in 1996. This is a case study of three schools that had engaged in Lesson Study for at least two years. The schools studied had a variety of geographical settings, socio-economic factors, community contexts, demographics, and organizational structures. Each school was recommended as an established representation of Lesson Study in action in an American school. All three schools had some level of interaction with Lesson Study practitioners from Japan. Teachers who engage in Lesson Study plan lessons together, observe each other teach the lesson, and then revise the lesson, seeking to "see the lesson through the eyes of the child" while "looking at the teaching, not the teacher". Through collaboration, distributed leadership, professional development, and feedback from colleagues, teachers strengthen their content knowledge and pedagogical skills to create effective lessons and to contribute to a professional learning community. The study shows that using Lesson Study builds relational trust between school stakeholder groups, promotes individual and organizational change through engaging in a professional learning community, and facilitates teacher-driven instructional improvement and improved student learning in mathematics. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]