The purpose of this study is to compare multiple measures of mathematics achievement for 1,378 cohort students who attended the same high school in a district from 9th to 12th grade with non-cohort students in each grade level. Results show that mobility had an impact on math achievement. After accounting for gender, ethnicity, and SES, adjusted mean scores on three large-scale achievement tests and adjusted average math grades were significantly higher for the cohort than the non-cohort. In terms of course-taking, larger percentages of cohort versus non-cohort students took advanced math courses in 11th and 12th grades. However, after controlling for gender, ethnicity, and SES, the impact of mobility on the type of math course taken was negligible. The study also examined math coursework over the four years of high school for cohort students. Differences were found across demographic subgroups with regard to the type of courses taken and cumulative math grade point average. Significant gaps were found between the two SES groups for both Black and White students in terms of the percentages of students taking advanced math courses. (Contains 5 tables and 1 figure.)