Data from a national sample of high school sophomores in 1980 from the High School and Beyond project show that senior-year mathematics test scores are highly dependent on the number of courses taken in mathematics, Algebra I or above. Within each level of course taking, senior test scores are predicted reasonably well from student socioeconomic status, sophomore-year verbal test scores, and sophomore-year mathematics test scores. The results support the theses that (a) whether black or white, female or male, sophomore students with similar levels of mathematics achievement may be expected to experience similar levels of improvement by taking additional mathematics courses and (b) the expected improvement is elevated for students with four or more credits of advanced mathematics or with three credits that include calculus.