This case study was designed to investigate the implementation of flexible grouping at one elementary school framed within the Change Based Adoption Model. Using interviews and observations, data were compiled to answer research questions related to the steps taken to implement flexible grouping, challenges faced, overall effects of flexible grouping, and a description of flexible grouping in practice. Interviews were conducted with administrators and focus groups. Observations were conducted of first grade teachers' reading classrooms. Themes emerged from the study that included concern from teachers in regards to change in practice, the need for a professional learning timeline for any new implementation plan, training for classroom management, and monitoring by administrators. For district and campus administrators this case study provides a framework in which to implement lasting change in instructional practice. [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/en-US/products/dissertations/individuals.shtml.]