The purpose of the present study was to examine the effects of 3 school-related constructs-motivation, attitude, and academic engagement-on 8th-grade students' achievement in mathematics and science. Although cognitive abilities of the students and their home backgrounds are important predictors of achievement, in recent years affective variables have emerged as salient factors affecting success and persistence in mathematics and science subject areas. The authors used the nationally representative sample of 8th graders drawn from the National Education Longitudinal Study 1988. They used structural equation models to estimate and test the hypothesized relationships of 2 motivation factors, 1 attitude factor, and 1 academic engagement factor, on achievement in mathematics and science. Results supported the positive effects of the 2 motivation factors, attitude and academic time on mathematics and science achievement. The strongest effects were those of academic time spent on homework.