School district officials have faced the urgent task in recent years of ensuring that all schools, not just a lucky few, benefit from sure-footed leadership by professionals who know how to focus on instruction and improve it. The question boils down to this: How can districts develop a pipeline of great school principals? Research about a Wallace Foundation school leadership initiative provides insights that may offer districts a way forward, as described in this Wallace "Perspective." Most important, the research finds that it is possible for districts to put in place the four key parts of a strong principal pipeline: apt standards for principals, high-quality pre-service training, rigorous hiring procedures, and tightly aligned on-the-job performance evaluation and support. Moreover, commencing to build a pipeline can produce several swift benefits for districts and principals alike. These include principal job standards that foster a districtwide understanding of what constitutes effective leadership for local schools, a possible greater compatibility between principals and the schools to which they are assigned, and performance evaluations designed not only to measure what's important but also to help principals succeed at their very tough jobs. At the same time, the research makes clear that some elements of the pipeline are harder to construct than others. For example, it's simpler for districts to upgrade their own training programs for aspiring principals than it is to work with universities to improve university-based programs. This "Perspective" offers a set of considerations for districts interested in building principal pipelines, as well as for states that want to help localities in this work. This publication draws from a number of sources, but chiefly from an independent evaluation of the implementation of Wallace's Principal Pipeline Initiative, an $85 million venture launched by Wallace in 2011 and under way in six large school districts.