School attendance zone boundary (AZB) data remain relatively underdocumented and understudied within the field of education, despite their critical implications for educational (in)equity. AZBs shape student outcomes and residential sorting patterns both by determining the public schools a student is assigned to and by signaling neighborhood characteristics to prospective homebuyers. The limited access, regulation, and review of AZB data to date has left a gap in the knowledge base, having the potential to leave intact (and exacerbate) patterns of segregation that maintain inequities in educational opportunity. Lack of data also limits our ability to know whether and when AZBs may mitigate segregation. In this brief, we examine a novel data collection effort of current and historical AZB data—the Longitudinal School Attendance Boundary System—to explore the contextual and political factors associated with data access and data quality. We aim to show how factors that hinder access to quality AZB data affect the study of educational equity, and we advocate for more comprehensive, top–down governmental efforts to create, maintain, and collect these data.