Aspiring principals often lack the training to improve teaching and raise achievement in troubled urban schools. This report finds that districts can influence universities to revamp principal preparation by acting like “discerning customers” who clearly communicate criteria for the school leaders they want to hire. It examines how eight Wallace-supported school districts went about improving principal preparation by setting hiring standards, collaborating with universities to redesign training or even organizing their own competing preparation programs. It describes a number of promising practices, such as strategies for identifying talented candidates for preparation programs and structuring internships for those enrolled. It also uncovers weaknesses in these efforts, including the difficulty of sustaining district-run programs and the absence of systems for evaluating the job performance of university program graduates. Finally, the report draws implications for policymakers, particularly the need for states to consider making substantial, long-term investments in high-quality principal preparation.