The purpose of this study was to examine the efforts of school districts in developing and sustaining their capacity to improve student achievement in response to increased accountability. The study sought to confirm what the research says regarding the role of the school district in influencing school improvement. While there is a significant body of research identifying elements for turning around low-performing schools, limited information exists on the roles of school district leaders in influencing school improvement. The study employed comparative case study methodology to examine the details of two school districts that had engaged in turning around low-achieving schools through the viewpoint of the study's participants (superintendents, assistant superintendents, district leaders overseeing school improvement, and school principals). This study identified the roles and practices of district leaders and determined the strategies used to successfully turn around low performing schools and sustain higher achievement. Increasing achievement across schools necessitates considering how school districts support school improvement and sustain district capacity to improve student achievement. Based on the findings, the study offers recommendations for district leadership practice in supporting school improvement and school turnaround. [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.]