This longitudinal study examined the outcomes of Project Excite on reducing minority students’ achievement gaps in STEM over 14 years. Project Excite was designed to provide intensive supplemental enrichment and accelerated programming for high-potential, underrepresented minority students from third through eighth grades to better prepare them for advanced math and science courses in high school. This study compared the performance of Project Excite participants with that of students from their local school districts and the state on the Illinois Standards Achievement Test, the Explore test, the Measures of Academic Progress, and on rates of placement in above-grade-level math courses in ninth grade. Project Excite participants consistently outperformed their Black, Latino, and low-income peers, and they came close to the performance levels of White, Asian, and non-low-income students. They were more likely to be placed in above-grade-level math courses than their minority peers in ninth grade.