Background/Context Research links advanced mathematics course-taking to important later outcomes, including college graduation and earnings, yet many students fail to progress into higher math courses as they move through high school. Black and Hispanic high school students are less likely than their white peers to take advanced math courses. A complex set of factors inform decisions about student course-taking, but teachers play key roles, including providing information about courses, giving students encouragement, helping students form aspirations (e.g., through role modeling), and serving as gatekeepers via grade assignment and formal recommendations. At the same time, growing empirical evidence suggests that students from different racial/ethnic groups benefit from being taught by teachers with similar demographic backgrounds, which motivates an analysis connecting math teacher–student racial or ethnic congruence with progression into higher math courses in high school. Purpose We investigate the degree to which having a math teacher of the same race or ethnicity predicts subsequent enrollment in more advanced high school math courses, as well as in honors and Advanced Placement (AP) math courses. We also investigate potential mechanisms, including impacts of student–teacher congruence on course grades and standardized test performance, which may in turn predict a higher likelihood of advanced math course enrollment. Setting We examine student-level administrative data from high schools in Miami-Dade County Public Schools, the fourth largest school district in the United States. Research Design We estimate the likelihood that a student will take a higher level math course as a function of student–teacher racial/ethnic congruence, plus student, teacher, and classroom characteristics, and school fixed effects. This research design compares later math course-taking between students with and without race/ethnicity-congruent teachers within the same school, holding a variety of other factors constant. We estimate similar models for honors and AP course-taking. We also estimate models for math course grades and end-of-course (EOC) exam scores using school-by-course and student fixed effects. Findings/Results We find that high school students with a same-race or same-ethnicity teacher are more likely to take a higher math course in the next year than other students taking the same course in the same school. Associations are largest for Black students, who are 2 percentage points more likely to advance to a higher math course when taught by a Black teacher. Having a demographically similar teacher is also associated with movement into honors and AP courses in the next term, on average, though results vary by student subgroup. Students receive higher EOC scores and higher grades when taught by a demographically similar teacher, with higher grades even than what would be predicted by their EOC score, particularly in algebra. Conclusions/Recommendations Our analysis contributes to growing evidence on the importance of teacher diversity for outcomes for students from minoritized groups and is among only a very small set of studies that demonstrate teachers’ impacts on student outcomes not just for one year, but also in subsequent years. Our results underscore the importance of efforts to recruit and retain teachers of color, particularly in high schools. We recommend future research to better understand the mechanisms linking diverse teachers to student course-taking outcomes.