The authors report 1-year outcomes for 11 children (3-7 years) with autism who attended an "Applied Behavior Analysis (ABA) classroom" educational intervention in a mainstream school setting. The children learned new skills by the end of 1 year and learned additional skills during a 2nd year. Group analysis of standardized test outcomes (IQ and adaptive behavior) showed moderate to large effect size changes over 1 year, with further changes during a 2nd year. Standardized test outcomes for nine children after 2 years were also analyzed against a comparison group (n = 18) of children with autism receiving "education as usual." These controlled comparisons were associated with statistically significant large effects in favor of the ABA group for adaptive skills. Exploratory analysis also showed that increases in language and learning skills in the ABA class group were generally associated with positive changes in standardized test scores. A comprehensive behavioral intervention model can be successfully implemented in a mainstream school setting.