A recent structural model suggests that nine factors exert both indirect and direct effects on seventh-grade mathematics achievement and attitude. The model was further tested with a national probability sample of about 2,500 high school sophomore mathematics students. A three-wave longitudinal design incorporated data from students, teachers, and parents. The structural model, evolved and cross-validated with the younger sample, significantly and substantially accounted for variance in mathematics achievement and attitudes toward mathematics. Although the magnitude of effects differed in some cases from the previous model, all structural correlations of achievement and attitudes with the productivity factors, 15 of 15 total effects and 18 of 18 structural effects, conformed to theoretical expectations of the model. Corroborating previous findings, home environment and previous achievement had the largest effects on achievement, perhaps because they cumulate during the preschool and elementary school years. Nonetheless, the other hypothesized factors—motivation, mathematics attitude, peer environment, amount and quality of mathematics courses, and classroom environment also had significant effects on outcomes.