This report from the RAND Corporation shares findings from an analysis of the Wallace Foundation’s University Principal Preparation Initiative, which provided grants to seven universities and their partners to redesign their principal preparation programs in line with research-supported practices. Key findings included: (1) collaboration between districts and programs inspired improved leadership development practices in districts; (2) districts developed data systems to identify, grow, and track leaders; and (3) successful district–program relationships were predicated by preexisting relationships and a focus on building a culture of trust and collaboration. The report ends with a series of recommendations for school districts seeking to develop stronger leaders and a stronger relationship with a principal preparation program, while also offering insight for preparation program administrators.