The third in a series of reports evaluating a multi-year Wallace initiative documents ways in which six districts are working to improve school leadership districtwide. It describes several new measures districts are implementing, including systematic support for assistant principals; the use of performance standards to hire and evaluate principals, as well as to inform training and support for them; and the establishment of data systems to promote more effective hiring, identify principals in need of support and provide feedback to the programs that trained them. This report is not the last word on the Principal Pipeline Initiative. Future reports on implementation and on effects will assess the actions taken by districts and their partner institutions in this initiative. A special-focus implementation report in 2015 will analyze principal evaluation systems. A 2016 report will assess implementation of the initiative overall, identifying the structures and policies put in place, the results observed, and factors that have supported or impeded the sites' progress in carrying out their plans. The reports also contains the following appendices (1): Survey Weighting and Analyses; and (2): An Exploratory Comparative Analysis. [For Volume 1 in this series, see ED555867; for Volume 2, see ED555868.]