Competitive debate programs exist across the globe, and participation in debate has been linked to improved critical thinking skills and academic performance. However, few evaluations have been able to adequately address self-selection into the activity when examining its impact on achievement. This study evaluated the relationship between participating in a debate program and academic performance among high school students (N=35,788; 1,145 debaters and 34,643 non-debaters) using linked debate participation and academic record data from the Houston Independent School District. Academic performance was indicated by cumulative GPA and performance on the SAT college entrance exam. Selection into debate was addressed using propensity score methods informed by sociodemographic characteristics and 8th grade standardized test scores to account for pre-debate achievement. Debate participation was associated with 0.66 points (95% Confidence Interval (CI): 0.64, 0.68) higher GPA, 52.43 points (95%CI: 50.47, 54.38) higher SAT Math, and 57.05 points (95% CI: 55.14, 58.96) higher SAT Reading/Writing scores. Findings suggest that competitive debate is associated with better academic outcomes for students.