To probe a psychological theory of educational productivity, background measures along with mathematics test scores and motivational measures of over 7,000 students (9-, 13- and 17-year olds from National Assessment of Educational Progress samples) were statistically related to each other and to indicators of constructs that prior research shows are associated with learning outcomes. Covariance structure analysis methods were used to evaluate the causal relation among student background characteristics, motivation and achievement measures. Results of this study indicate the importance of the student motivation factor in understanding student learning outcomes. The role of motivation as an educational productive factor became more important for students as they increased in age from early adolescence to late adolescence. The influence of home background on achievement was significant at all ages while also showing a more general positive relationship over the adolescent years. (Author)