This qualitative case study explored how educators in a high-poverty, urban public high school used student achievement data to inform instruction. The sample consisted of one principal, five counselors, and ten teachers across multiple departments in a Los Angeles County high school recognized for its data-driven practices and collaborative culture. Data were collected through interviews with the principal, two counselors, and four English teachers, as well as observations of various meetings and co-planning sessions. Findings highlighted a shift from a "data-driven" to a "data-informed" approach, where data serves as a guide rather than a mandate. The study revealed that strong leadership, particularly from the principal, and structured collaboration, especially within Professional Learning Communities (PLCs), fostered a supportive environment for data use. This environment empowered educators to contextualize data within their unique classroom settings. However, variability in data engagement across departments underscored the need for sustained professional development. This study contributes to understanding how school culture, leadership, and resources shape data-driven decision-making, identifying both enablers and challenges educators face in their use of data. The results suggest that data use is most effective when embedded within a collaborative and supportive school culture that values professional judgment and contextual understanding alongside technical data analysis. [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.]