Recent research on implementation and effects demonstrates the important difference comprehensive and aligned principal pipelines can make in districts and schools. The implementation studies analyzed in depth how school districts can strategically put in place policies, processes, and infrastructures to strengthen school leadership. Research on achievement effects showed that schools in these districts with newly placed principals outperformed comparison schools to a statistically significant and meaningful extent over three years. This guide is built on the research evidence. Because many districts have already put in place key pipeline elements and want to know where there is room for improvement, this guide was created to help districts reflect on their policies, processes, and infrastructures related to school leadership and begin planning for improvement. It provides a set of evidence-based indicators of pipeline functioning and a framework for applying the indicators through self-study. Districts rate their own status on each indicator as a step in their decision making and planning. This guide is designed to help in improving any school district's principal pipeline, recognizing that structures for advancement and support differ across districts. The guide encourages district decision makers to consider the quality of the design and implementation of their own structural arrangements and how well these work as a system. Districts that have principal pipelines find that alignment across the domains of leadership development lends important coherence to their work and can advance district-wide progress.