School is often considered an ideal setting for child social skills training due to the opportunities it provides for skills teaching, modeling, and practice. The current study evaluated the effectiveness of two variants of the Secret Agent Society social skills program for children with high-functioning autism spectrum disorders (HFASD) in a mainstream school context. Sixty-nine students aged 7-12 took part in one of two different 10-week versions of the program (structured versus unstructured) to determine their relative effectiveness. Results suggested that both program variants led to improvements in emotion regulation abilities, social skills, and behavior at school and home, maintained at 6-week follow-up. However, the structured intervention generally led to superior treatment outcomes. These results suggest that improvements in social-emotional functioning can be achieved for students with HFASD through time-limited school-based interventions. Limitations of this study and directions for future research are discussed.