Drawing on the expectancy-value model, stage-environment fit theory, and self-determination theory, this study examined the longitudinal associations between classroom characteristics, expectancies-values, high school course enrollment, and career aspirations in the domain of math. Data were collected on 3,048 youth who reported on their classroom experiences in 7th grade, expectancies-values in 6th, 7th, and 10th grades, and career aspirations in 12th grade. Student grades for math courses were collected from school records at 6th, 7th, and 10th grades, and their math course enrollment was collected from 9th through 12th grades. Results indicated that students' math classroom experiences predicted their expectancies and values, which, in turn, predicted the number of high school math courses taken and career aspirations in math. Gender and math ability differences are also discussed. (Contains 4 tables and 3 figures.)