A prior cluster randomized controlled trial (RCT) compared outcomes for a comprehensive school intervention (schoolMAX) to typical educational programming (services-as-usual [SAU]) for 103 children with autism spectrum disorder (ASD) without intellectual disability. The schoolMAX intervention was superior to SAU in improving social-cognitive understanding (emotion-recognition), social/social-communication skills, and ASD-related impairment (symptoms). In the current study, a range of demographic, clinical, and school variables were tested as potential moderators of treatment outcomes from the prior RCT. Moderation effects were not evident in demographics, child IQ, language, or ASD diagnostic symptoms, or school SES. Baseline externalizing symptoms moderated the outcome of social-cognitive understanding and adaptive skills moderated the outcome of ASD-related symptoms (no other comorbid symptoms or adaptive skills ratings moderated outcomes on the three measures). Overall, findings suggest that the main effects of treatment were, with two exceptions, unaffected by third variables. [This paper was published in "Journal of Abnormal Child Psychology" v48 p1105-1114 May 2020.]