At a 20/1 pupil/teacher and pupil/room ratio, by 1984 Iowa public schools will need 8,100 fewer rooms and teachers than was necessary during the peak enrollment year of 1969. The most precipitous drop in enrollment could come in the six year period from 1977 to 1982 when 120,363 more students will graduate from the public school system than will enter it. The drop in Iowa enrollment can be partly explained by a significant out-migration since 1930, an out-migration which drains disproportionate numbers of the 20-29 age group, the future parents of school children. Population has also shifted within the state; both the largest cities and rural areas are losing population to the suburban fringe around major industrial centers. This study traces Iowa enrollments historically, explores the cause for cycles of change, projects enrollments to 1982 and 1987, and examines the impact of enrollment trends upon Iowa public education. Because enrollment projections can be no more reliable than the causative data which determine school enrollment trends, the document also traces such factors as (1) population growth, (2)out-migration from the state and between counties, (3) relative proportion of significant age groups in the population, (4) trends in fertility rates and births, (5) enrollment trends and projections, (6) geographical trends in enrollment and (7) enrollment trends by size of school. Tabular data includes 1969 and 1977-78 enrollments and projected enrollments (1982-83 and 1987-88) for each Iowa public school. (Author/DS)