The model has 4 stages. See figure 71 . Enrollments by age and age groups from the Bureau of the Census were adjusted to NCES totals to compute enrollment rates for 1972 through 1994. Different assumptions were made to produce low, middle, and high alternative projections of enrollment rates to the year 2007. Elementary Grades 1-8 Projections of elementary enrollment rates were considered for ages 5 through 18.
Elementary enrollments are negligible for the remaining ages.
Because most elementary enrollment rates have been close to 100 percent from 1972 to 1994, alternative enrollment rate projections were not computed. Several of the rates in table A1.1 exceed 100 percent, as a result of several factors. The enrollment data by age were prorated to agree with NCES totals. The Bureau of the Census does not revise enrollment estimates by age, but population estimates are revised regularly. Secondary Grades 9-12 Projections of secondary enrollment rates were considered for ages 12 through 34.