Fourteen tables and four graphs present data on 1971-82 enrollment changes in Illinois public elementary and secondary schools for the state, county, and school district levels. Changes in the statewide enrollment of racial and ethnic minority groups are also examined for the same period. The authors discuss factors affecting Illinois enrollment changes--including births since the 1940s, population migration, and nonpublic school enrollments--and make estimated projections of enrollments through 1996. Among the study's findings are that Illinois has experienced greater enrollment decline than the nation as a whole; all but four Illinois counties have had enrollment declines; the chief factor causing Illinois enrollment changes has been the drop in births from about 1960 to 1975; and Illinois public school enrollments will continue to decline through 1990 but will increase gradually thereafter until about 1996. (Author/RW)