Federal mandates have increased the pressure on school officials to improve student achievement. These mandates have forced educators across the nation to analyze different types of professional development that train teachers to provide quality lessons that are rigorous in nature. These mandates have forced a shift in pedagogy where teachers work collaboratively as opposed to working in isolation. This study examined the Lesson Study Process and the impact it had on teacher pedagogy. Also examined was if there was an increase in teachers' knowledge on how students learn when they participated in the Lesson Study Process. Lesson Study, originally from Japan, is a form of professional development that fosters collaboration. Lesson Study gives teachers the opportunity to plan, teach, observe and critique their practice and the practice of their colleagues. When complete, the teachers in this study gained a better understanding of the delivery of instruction that had an impact on student achievement. The targeted population for this qualitative research study was four teachers from a private school setting. The teachers were divided into two teams. One teacher team consisted of two teachers in the lower grades and the other teacher team consisted of two teachers in the upper grades. Qualitative data from observations of lessons, two focus groups, questionnaires, artifacts, and formative data was examined to identify common threads within the research questions. Those common themes included common planning time, observing practice and reflection. Results from the qualitative data indicated that the teachers who participated in the Lesson Study Process felt that the process significantly impacted their pedagogy. Results provided specific examples of the Lesson Study Process and how its components impacted teacher practice. Results from this study add evidence to current research that Lesson Study is a form of professional development that impacts teacher effectiveness when delivering instruction. Additionally, results also provide suggestions that student achievement is impacted when teachers participate in the Lesson Study Process. Results support the utilization of Lesson Study as a form of professional development for teachers. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]