In 1960, ascertained for persons 5 to 34 years of age, who were classified as enrolled in school if they attended regular school or college at any time since February 1, 1960. (Attendance at a nursery school, business or trade school, or adult education classes was not to be counted; regular schooling included kindergarten and schooling leading to an elementary school certificate, high school diploma, or college degree.) Persons enrolled in a regular school who did not actually attend because of illness, etc. were classified as enrolled in school. In 1970, ascertained for persons 3 years and older, who are classified as enrolled in school if they attended regular school or college at any time since February 1, 1970. (Regular schooling includes nursery school, kindergarten, and schooling leading to an elementary school certificate, high school diploma, or college degree.)

Persons enrolled in school were asked the year or grade in which enrolled up to 6 or more years of college. In 1960, enrollment was classified into four levels with separate years or grades identified within each level as indicated below. In 1970, enrollment is classified as in 1960 with the addition of nursery school.

Persons enrolled in school are classified by type of school in terms of public or private, as indicated below.

In 1960, ascertained for persons 5 years of age and over; in 1970, for persons 3 years of age and over, who were asked the highest grade or year of regular school they ever attended up to 6 or more years of college, Persons attending school were asked the year they were completing. Persons were also asked whether they finished the year specified as the highest grade attended (or were attending that year).

The number tabulated in each category of years of school completed includes persons who report completing that grade or year plus those who attended but did not complete the next higher grade. A common breakdown is no school years completed; 1-4, 5-6, 7, 8 years elementary; 1-3, 4 years high school; 1-3, 4 academic years or more college. Single years of the highest grade attended are carried on census basic records. Tabulations are commonly produced for particular age groups such as persons 14 and over, persons 25 and over, persons 14 to 24 not enrolled in school.

Median school years completed is calculated as the value which divides the population in half, Years of school completed statistics are converted into a continuous series: the first year of high school becomes grade 9, the first year of college grade 13, etc. Persons who have completed a given year are assumed to be evenly distributed from .0 to .9 of the year. For example, persons who have completed the 12th grade are assumed to be evenly distributed between 12.0 and 12.9.

Not asked in 1960. In 1970, ascertained for persons 14 to 64 years of age who were asked whether they ever completed a vocational training program; for example, in high school, as an apprentice, in a school of business, nursing, or trades, in a technical institute, or an Armed Forces school. Respondents were also asked to indicate the main field of such training as follows: business, office work; nursing, other health fields; trades and crafts; engineering or science technician, draftsman; agriculture or home economics; other field. Vocational training does not include courses received by correspondence, on-the-job training, or Armed Forces training not useful in a civilian job.