The use of analyses of achievement test data, particularly longitudinal data, in a wide range of court cases bearing upon educational policy and practice is examined, with an emphasis on assessments of the educational progress of students. The main purpose of the project is to show that assessments of educational progress (i.e., student learning) are integral to many court cases and related educational policy issues. Project participants were educational researchers and specialists in quantitative methods. The major research questions addressed the types of questions about student progress that arise in educational court cases, the types of data and statistical summaries that are presented in court cases, courts' responses to the empirical evidence on student progress, and presentations that prove most successful. The representation of academic progress by student growth in achievement, the definition and representation of expected growth, and data and methods used in practice to assess student progress are discussed. Specific educational court cases involving the measurement of student progress are presented covering the evaluation of teacher performance, racial discrimination, mandated desegregation, and student classification. Reanalyses of the evidence presented in two cases are also described. Finally, suggestions are made for improved data collection, data management, and statistical analysis. A 61-item list of references, an annotated bibliography of additional sources, and two computer programs for analyzing student progress are included. (TJH)