This large-scale study identified evidence of positive relationships between school music participation and high school exam scores in English, mathematics, and science using population-level educational records for over 110,000 students in British Columbia, Canada. Participation in school music (especially instrumental music) was related to higher exam scores, and students with higher levels of school music engagement had higher exam scores. The positive relationships between music engagement and academic achievement were independent of students’ previous (Grade 7) achievement, sex, cultural background, and neighborhood socioeconomic status, and were of considerable magnitude: The group differences observed in our study were greater than average annual gains in academic achievement during high school. In other words, students highly engaged in music were, on average, academically over 1 year ahead of the peers not engaged in school music. In light of this study (the largest of its kind to date), as well as supporting evidence suggesting music learning in childhood may foster competencies (e.g., executive functioning) that support academic achievement, educators may consider the potential positive influence of school music on students’ high school achievement.