The question examined in this paper is whether variability in the quantity of schooling students receive in different curricular areas is a contributor to observed differences in achievement not only among students attending different high schools, but among students in the same high school. A conceptual framework enumerates the determinants of achievement, including school and community characteristics, student background, and quantity of schooling in the specific curricular areas of mathematics, English, foreign language, fine arts, social studies, and science. The sample used was 9,195 high school seniors in 725 schools taken from the National Longitudinal Study of the High School Class of 1972, a nationally representative probability sample of high school seniors. The results suggest that quantity of schooling has a positive effect on academic achievement. The more the achievement is school-related, the larger is the resulting effect of the quantity of schooling. This was especially true for mathematics. Quantity of schooling also had positive effects on achievement in science and English; less clear results were found in the areas of vocabulary and reading comprehension, although quantity of schooling did continue to have a positive effect on achievement. (Author/MLF)