“The Expanded Success Initiative: Challenges and Progress in the Pursuit of College and Career Readiness for Black and Latino Young Men” synthesizes findings from the Research Alliance’s four-year evaluation of Expanded Success Initiative (ESI). This report, draws on hundreds of interviews and focus groups with ESI school leaders, teachers, and students; annual questionnaires and rubrics to assess programming in ESI schools; a survey administered to over 5,000 students each year in ESI schools and a set of matched comparison schools; and administrative records for students in both sets of schools. This document is a companion to the full report and provides a description of the high schools that were selected to participate in the Expanded Success Initiative, focusing on the background characteristics and performance of students who entered the schools prior to the start of ESI. It also describes the matching process used to identify an appropriate set of comparison schools for the evaluation of the initiative. Appendix B provides an ESI programming alignment rubric. Appendix C presents the analytic method for focus group and interview transcripts. Appendix D provides student survey response rates, baseline equivalence and item-by-item construct lists. Supplemental tables for Chapter 4 student participation in ESI-related activities are contained in Appendix E. Appendix F provides supplemental tables for Chapter 6. Appendix G describes the technical specifications of the statistical models that were used to generate estimates from the comparative interrupted timeseries (CITS) analysis. Supplemental tables for chapter 6 — ESI impacts on attendance, suspension, graduation and college enrollment are contained in Appendix H