This appendix volume supplements Evaluation Report NCEE 2025-006r, which assessed whether families' expressed interest in and use of scholarships for the Opportunity Scholarship Program (OSP) appears consistent with the goal for program expansion. Appendix A provides additional information about the Opportunity Scholarship Program (OSP), including key features of the program, its origins in the DC School Choice Incentive Act and its reauthorization under the Scholarships for Opportunity and Results (SOAR) Act in 2011 and 2017. It also includes an overview of the findings from two prior Congressionally mandated evaluations of the program, which serve as the basis and motivation for the current study which focuses on the program's implementation since it's reauthorization in 2017. Appendix B describes how this study was designed and carried out to provide more information about the trends in: (1) who applied for an OSP scholarship in one of the six "application years" after the OSP was reauthorized through the SOAR Act of 2017 (2016-17 to 2021-22); and (2) who used an offered OSP scholarship in one of the following "enrollment years": 2017-18 to 2022-23. Appendix C presents additional details on the findings in the report. The underlying counts and percentages presented in this section were used to generate the exhibits on expressed interest in the OSP, the use of an offered OSP scholarship, the use of an offered OSP scholarship by applicants' grade and racial or ethnic backgrounds, and the DC public school options available to OSP applicants. Appendix D presents supplemental findings not included in the report to provide new information for interested readers. While not the focus of the report, the study examined the relationship between students' grade level, race, and ethnicity and their expressed interest in the OSP and scholarship use. Understanding these characteristics of students who expressed interest in the program and used an offered scholarship provides information about those who find the program appealing.