These appendixes provide supplemental detail about the analyses and findings presented in Preparing School Leaders for Success: Evaluation of New Leaders' Aspiring Principals Program, 20120-2017 (Gates et al., 2019). This material will be of interest to technically oriented readers who seek more information about the information presented in the main report. Appendix A provides profiles of New Leaders partner districts. Appendix B contains detailed information on our analysis of school-level outcomes. Appendix C presents technical details about our analysis of student achievement outcomes using student fixed-effects models. Appendix D describes our analysis of principal retention. Appendix E provides details about our analysis of correlations between Aspiring Principals program competency metrics and outcomes. [For the full report, see ED605722.]