This study examined the relationship between strong instructional leadership, as measured by the Principal Instructional Measurement Rating Scale (PIMRS) and high student academic outcomes in 35 Mid35-Atlantic Catholic elementary schools. In addition, the research explored the role of Catholic identity in supporting instructional leadership behaviors in Catholic elementary schools. The purpose of the study was to examine. A) instructional leadership behaviors in principals with high versus low student academic outcomes, and B) to use a measure of Catholic identity to differentiate the extent to which principals can focus on instructional leadership. This research focused on ways Catholic schools can both improve themselves and inform charter and traditional public schools. The study consisted of over 100 principals and teachers in Mid-Atlantic Catholic elementary schools. The participants completed the PIMRS and Framework for Catholic Identity (FCI) to identify instructional leadership behaviors and level of Catholic identity. To document student academic achievement in aggregate, the research used a value added growth model. Using factor analysis, the researcher identified behaviors associated with schools in different levels of student growth and performance on standardized assessment in relation to outcomes on the PIMRS and FCI. Research on principal leadership behavior is extensive and focuses on either traditional public schools, using an instructional leadership model supported by top-down leadership or public charter schools that focus on transformational leadership. The research provided evidence that Catholic schools reside in between instructional and transformational leadership, with Catholic culture supporting instructional leadership. Since Catholic schools lack an organized and systemic top-down leadership model, there is a gap in knowledge of the unique environment of site-based leadership management in Catholic schools. In addition, the research informs school improvement across all sectors of K-l2 education. This research is designed to identify best practices in site-based leadership, as practiced in Catholic (P)K-8 elementary schools, to help improve education in public, charter, and non-public schools. With many organizations, such as the Bill and Melinda Gates Foundation, supporting transformational leadership model to expand charter school across the country, there is a need to understand in what context it is possible to scale a site-based leadership model. Catholic schools benefit from having a Catholic culture drive their goals and purpose, which unlike charter schools, is not dependent on a single person or group. The implications of this study will inform Catholic school central offices on principal behaviors within its unique structure. In addition, the research will inform school reformers on how to harness the most effective elements of both instructional and transformational leadership to improve student academic outcomes for all students. [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.]