This research is part of a comprehensive effort to pinpoint the key leadership factors that improve student achievement and increase the number of high school graduates who are ready for college and careers. In this study, SREB (Southern Regional Education Board) examined the role of the district office in providing principals with the working conditions they need to improve teacher effectiveness and student performance in the middle grades and high school. This investigation included 35 interviews with superintendents, school board chairs and selected central-office leaders from seven diverse school systems in three SREB states. The research design was shaped in part by earlier SREB studies that analyzed principals' perceptions of the support they receive from higher up in the school governance structure. The findings in this report include two overarching conclusions: (1) Three essential elements must be in place for struggling high schools to improve in substantive ways: State capacity-building, district vision, and principal leadership; and (2) These elements are rarely all present and working in sync. The result of SREB's work is a set of seven strategies that supportive districts can use to help their middle grades and high school principals succeed in improving student achievement and the learning environment: (1) Establish a clear focus and a strategic framework of core beliefs, effective practices and goals for improving student achievement; (2) Organize and engage the school board and district office in support of each school; (3) Provide instructional coherence and support; (4) Invest heavily in instruction-related professional learning for principals, teacher-leaders and district staff; (5) Provide high-quality data that link student achievement to school and classroom practices, and assist schools to use data effectively; (6) Optimize the use of resources to improve student learning; and (7) Use open, credible processes to involve key school and community leaders in shaping a vision for improving schools. (Contains 9 tables and 37 footnotes.)