The data on grade or level in which enrolled were derived from long-form questionnaire Item 8b, which was asked of a sample of the population. People who were enrolled in school were classified as enrolled in "Nursery school, preschool," "Kindergarten," "Grade 1 to 4" or "Grade 5 to 8," "Grade 9 to 12," "College undergraduate years (freshman to senior)" or "Graduate and professional school (for example: medical, dental, or law school)."
Grade of enrollment was first available in the 1940 census, where it was obtained from responses to the question on highest grade of school completed. Enumerators were instructed that "for a person still in school, the last grade completed will be the grade preceding the one in which he or she was now enrolled." From 1950 to 1980, grade of enrollment was obtained from the highest grade attended in the two-part question used to measure educational attainment. (For more information, see the discussion under "Educational Attainment.") The form of the question from which level of enrollment was derived in the 1990 census most closely corresponds to the question used in 1940. While data from prior censuses can be aggregated to provide levels of enrollment comparable to the 1990 census and Census 2000, the data from these sources cannot be disaggregated to show single grade of enrollment as in previous censuses.
In the 1990 census, people who were enrolled in school were classified as enrolled in "preprimary school," "elementary or high school," or "college," according to their response to long-form questionnaire Item 12 (years of school completed or highest degree received). Those who were enrolled and reported completing nursery school or less were classified as enrolled in "preprimary school," which includes kindergarten. Similarly, those enrolled who had completed at least kindergarten, but not high school, were classified as enrolled in elementary or high school. The enrolled who also reported completing high school or some college or having received a post-secondary degree were classified as enrolled in "college." Those who reported completing the twelfth grade but receiving "NO DIPLOMA" were classified as enrolled in high school.
The Census 2000 question is the first to be asked only of the enrolled and does not serve to measure both year of enrollment and educational attainment. While the attainment item in 1990 served the needs for educational attainment data better than the question used in earlier censuses, it did not serve reporting of enrollment level well.