This case study examines how district administrators and high school mathematics and science teachers use data in instructional decision making and what challenges they face in the current accountability context. Findings reveal unique aspects of data use directly related to a high school setting within the context of test-based accountability and illustrate how overlapping systems (state and federal policy, subject area knowledge, district norms, etc.) influence data practices. We conclude with implications for practice and policy around ways to use data to inform instruction beyond passing state assessments.