...Representation The sample design involved 1,200 primary sample schools and 21,600 students (18 per school). Of the 1,200 primary sample schools, 948 participated in the base-year survey (spring 1972), 21 had no senior students enrolled, and 231 either refused to participate or could not,...

...those attending adult education classes were also excluded from the sampling. School Representation Of the 1,200 primary sample schools, 948 participated in the base-year survey, 21 had no seniors enrolled, and 231 either refused to participate or could not, if they had received the request...