Findings of a study that examined whether high school size significantly supplemented factors identified as contributing to educational achievement and ability are presented in this paper. In general, two divergent viewpoints concerning school size have been argued. One view holds that large schools are better than small schools because they offer students broader and richer curricula, larger libraries, and better facilities; the other view argues that small schools are better because they offer students more individualized attention. This study explored the effect of school size on Walberg's model of educational productivity (1984). Variables from the questionnaires used in the National Longitudinal Study (NLS) of the High School Class of 1972 were matched to the productivity factors identified by Walberg. The subjects were 1,539 senior high school students from the original 1972 study who were reexamined in 1979. The subjects were asked to take a test of ability consisting of selected mathematics and vocabulary questions from the 1972 test. Results indicated significant support for Walberg's productivity factors, which include ability, age, motivation, instructional quality and quantity, and home and classroom environments. School size was significant for educational attainment. The data argue that school size at the high school level is not an issue in educational ability and reaffirm the importance of the home environment in contributing to learning productivity. Three tables are included. (Contains ll references.) (Author/LMI)