The purpose of this improvement initiative, providing effective professional development focused on differentiated instruction, was to increase teacher capacity in addressing the needs of individual students at Swain County Middle School. This disquisition introduces the problem of practice, context of the problem, improvement initiative, and the iterative process to evaluate the effectiveness of the improvement initiative. In response to laws that promote equitable access to high quality content and standards, schools are abandoning homogenous groupings. Students from a variety of ethnic, economic, and educational backgrounds learn together in arguably the most culturally diverse classrooms in the history of education. However, instruction has not responded well to the increased diversity and the achievement gap has been slowly closing but remains pervasive and persistent. Swain Middle School (SMS) mirrors society with its gaps in achievement. In order to increase student achievement at SMS, a team of faculty facilitated professional development focused on differentiated instruction. This disquisition describes the three rounds of professional development, the improvement science method used, and the practical measures that gauged the effectiveness of the improvement initiative. [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.]