We analyze longitudinal data from students who spent their academic careers in North Carolina (NC) public secondary schools and attended NC public universities to investigate the importance of high school racial composition and opportunities to learn in secondary school for choosing a science, technology, engineering, and mathematics (STEM) major. We consider school racial composition and opportunities to learn as contexts that shape students' decisions regarding college majors. Results of cross-classified hierarchical logistic models indicate that attending schools with predominantly White students is negatively associated with declaring a STEM major and with graduating with a STEM major irrespective of students' own race. The finding suggests that for students in North Carolina, attending racially isolated White high schools is related to a decrease in adolescents' participation in STEM during college.