Relatively little is known about patterns of school-based supportive services for youth with autism spectrum disorder. This study describes these supportive services and their correlates, both cross-sectionally and retrospectively, in a large sample (N = 283) of 6- to 18-year-old youth. To assess whether special education designation and classroom placement patterns were peculiar to autism spectrum disorder, we also conducted analyses comparing youth with autism spectrum disorder to those with other psychiatric diagnoses (N = 1088). In higher grades, the relative quantity of three common supportive services received by youth with autism spectrum disorder decreased, while total supportive service quantity remained stable over time. Youth with autism spectrum disorder were more likely to receive a special education designation and were placed in less inclusive classroom settings than youth with other psychiatric diagnoses. These findings suggest that as youth with autism spectrum disorder reach higher grades, changes in service provision occur in terms of both time and quantity.