This research examines what educational administrators can do to help secondary teachers effectively use data to inform their instruction and improve their practice. This qualitative study focused on the interviews of principals and teachers in 14 secondary schools that have used data to improve their school's accountability measures markedly in the past three years. In researching this topic, I interviewed teachers and leaders on their practical experience using and promoting data-informed instruction at the secondary level. Precise instruction tailored to each student promotes a growth model of education that serves all students. The research questions focused on the link between data use and focused instruction in the secondary classroom and how can school leaders build a bridge between their leadership and teacher practice. The limitations of previous studies were that most of the studies used only primary schools' math and reading classes, and small sample size. This research implies that administrators could have a better understanding of how to support teachers across all subjects, and thus improve data use and focus instruction. Future research should emphasize methods to measure gains in learning with data informed instruction and the precision teaching model. There exists a lack of research on the links between data coaches and student outcomes. This future research could help improve perceptions of practices that are difficult to implement. This method along with what is known about collaboration, teacher capacity and leadership could allow school leaders to better understand their role in helping teachers to better implement data-informed instruction in classrooms. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]