This study tested the theory that an authoritative school climate characterized by disciplinary structure and student support is conducive to positive academic outcomes for middle and high school students. Multilevel multivariate modeling at student and school levels was conducted using school surveys completed by statewide samples of 39,364 students in Grades 7 and 8 in 423 middle schools and 48,027 students in Grades 9 through 12 in 323 high schools. Consistent with authoritative school climate theory, both higher disciplinary structure and student support were associated with higher student engagement in school, higher course grades, and higher educational aspirations at the student level in both samples. At the school level, higher disciplinary structure was associated with higher engagement, and higher student support was associated with higher engagement and grades in both samples. Overall, these findings add new evidence that an authoritative school climate is conducive to student academic success in middle and high schools.