The 1940 census included a question on the last full grade that the person had completed in the regular school system-public, private, or parochial school, college, or university. The tabulation of last grade or year of school completed for census tracts is restricted to persons 25 years old and over, practically all of whom have completed their formal education. In the computation of median years of school completed, the first year of high school is uniformly represented by 9, although there are some areas with only 7 years of elementary school.