This report presents data from three longitudinal studies conducted by the National Center for Education Statistics. The National Longitudinal Study of the Class of 1972, the High School and Beyond study, and the National Education Longitudinal Study of 1988 (NELS:88) were all designed to assess the educational experiences and achievements of high school students. With each study cohort, the scope of the study was enlarged until the three studies came to provide a rich resource for examining changes in U.S. education in the past 20 years. Enrollment in academic programs had declined from 1972 to 1980, falling from 46 percent to 39 percent, but by 1992, it had returned to its 1972 level, and 48% of seniors were in academic programs. The percentage of seniors in vocational programs has declined from 22% in 1972 to 12% in 1992. The rebound in academic program enrollment is caused primarily by higher enrollment rates among females and minorities. Differences in achievement among racial and ethnic groups are decreasing, but social class distinctions are becoming more marked. In 1992, more students planned to go to college than in 1972, and heightened expectations for graduate degrees became apparent for all racial and ethnic groups. Five appendixes provide 44 supplementary tables and an illustrative figure, information about study methodology, and a list of publications using NELS:88 data. (Contains 21 tables, 9 figures.) (SLD)