This study examined growth trajectories of teacher-reported adaptive behavior in a diverse sample of adolescents with autism spectrum disorder. The participants were 244 adolescents between the ages of 14 and 21 years who were assessed at up to four time points across two and a half years of high school. Demographic variables (age, sex, race, maternal education), phenotypic characteristics (intelligence quotient, autism severity) and school factors (location of the school, school quality) were collected. Growth mixture modeling was used to identify distinct classes of growth trajectories in communication, daily living skills, and socialization domains of adaptive behavior. Two distinct classes were identified for each domain. The first class had moderately low adaptive behavior scores and demonstrated growth of adaptive behavior over time and the second class had low adaptive behavior scores and did not demonstrate change over time. Adolescents within the moderately low adaptive behavior classes were younger at enrollment in the study, had higher IQs, and lower autism symptom severity. Logistic regressions were performed, and aspects of school quality predicted the likelihood of being in the moderately low classes above and beyond autism symptoms.