The Gifted and Talented program in New York City is one of the largest and longest running programs for gifted students in the nation. Yet little is known about its effects on student outcomes. Using student-level administrative data of New York City public school students between the 2010--2011 and 2018-2019 academic years, we studied the effects of the Gifted and Talented program on students' test score performance. Estimates from a matched comparison study show significant gains in middle school English language arts and math proficiency, after controlling for cohort, ethnicity, and district. Our balanced treatment and control groups provided sufficient sample sizes with which to analyze the performance of underrepresented minoritized groups, and we found significant treatment heterogeneity, where Black and Hispanic students showed the largest increase in academic proficiency scores after participating in the Gifted and Talented program. Implications of these findings for education policy--particularly related to new developments in selective school admissions--are discussed.