Although the number of high-needs schools that are failing to achieve "Adequate Yearly Progress" (AYP) steadily increases, some are successfully increasing student achievement, staff productivity and collegiality. The purpose of this study was to use a three-round Delphi process to obtain the expert opinions of 10 administrators who moved their schools from the No Child Left Behind (NCLB) rating of "Needs Improvement" to achieving AYP through effective use of data. The study was guided by four questions: what data tasks do administrators need to know and be able to do to make effective decisions?; what tasks did they actually perform?; what were the greatest barriers for completing these tasks?; and what were the greatest successes? Round 1 of the Delphi solicited administrator responses to the four opened-ended research questions. After coding and grouping the responses, 55 items emerged across the four questions. During Round 2, the administrators edited, deleted, and added to the 55 items. For Round 3, the administrators indicated if the final revised items should remain and indicated the importance of each item in relation the associated question. The results revealed three common themes among experts responses regarding critical data tasks administrators need to know to make effective decisions: interpret and use academic achievement data to revise instruction for all groups; align curriculum with standards, and achieve accountability from staff, students and parents. Whereas, the emergent categories for actual use of data were: disaggregating assessment data; meeting regularly with staff to determine implications for teaching and learning; and creating reliable performance profiles. One common theme emerged for barriers to implementing data-driven decisions, insufficient time to use data to guide school improvement strategies. For the fourth question, the two emergent themes regarding most successful strategies for making effective decisions around school improvement were the use of scientifically based strategies to improve student achievement and having celebrations for small and large gains to increase student achievement. In summary, as school districts strive to ensure that no child is left behind, the findings of this study have the potential to help school administrators more effectively use data to improve schools. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]