The recent concern with industrial achievement has reinforced a growing tendency to be concerned with educational achievement. This study, the first in a series, examined whether or not student motivation made a unique contribution to achievement that could be separated from other factors known or thought to contribute to student achievement such as various characteristics of the school. This study used data gathered by the Illinois State Board of Education and the University of Illinois in 1970 and 1981. High school juniors attending 120 schools were the subjects; the 1981 sample consisted of 9,693 students. Academic achievement, school context, family context, and student motivation were measured. Results suggest that variables composing the school context measure were least predictive of achievement variance and student motivation was the most predictive. Overall the expectation variable was the most predictive across all achievement domains. Family context cluster variables were important to school achievement across all subject areas. The results of this research illustrate the vital and critical role played by motivation in determining school achievement. (ABL)