Difficulty processing sensory information may impede progress in school for students with autism spectrum disorder (ASD). We explore the relationship between sensory processing and school performance in 26 high-functioning youths with ASD and 26 controls (age 8-14) using measures of sensory, social, cognitive, and academic functioning. In the ASD group, bivariate Pearson correlations indicated a significant positive relationship between intelligence quotient (IQ) and the School Competence Scale (SCS) of the Child Behavior Checklist (CBCL), and a significant negative relationship between Dunn's Sensory Processing Framework and SCS scores. Final hierarchical multiple linear regression model accounting for SCS scores in ASD included IQ, ADHD symptoms, and sensory features. An interaction between increased sensory sensitivity with reduced sensory avoidance behaviors explained the greatest amount of variance in SCS, meaning school performance is lowest for children with greater hypersensitivity and fewer avoidance behaviors. Results indicate a strong impact of sensory processing on school performance in ASD.