Establishing school-based drug prevention programs was the aim of the Drug-Free Schools and Communities Act of 1986 (DFSCA). The study design and data collection methods for a longitudinal study of the effectiveness of DFSCA are presented in this report. As part of an overall assessment of DFSCA, the report details the methodology used to accomplish the goals of the longitudinal study and it provides supportive evidence for the viability of the study design and the student sample. (The longitudinal study examines student behaviors and attitudes about alcohol and drugs, characteristics of school-based prevention programs in the participating school districts, and the effectiveness of those programs.) Same-grade comparisons are reported on drug use, attitudes, and perception of drug use for a cohort of two age-groups. These comparisons, which serve to establish the validity of the data, also afford a unique look into the potential age-related tendencies for the reported drug use behaviors and attitudes. The student survey instrument is appended. (EMK)