There are inconsistent findings regarding parent and teacher agreement on behavioral ratings of their children with autism. One possible reason for this inconsistency is that studies have not taken autism severity into account. This study examined parent and teacher concordance of social behavior based on symptom severity for children with autism. Participants were 123 parent-teacher dyads who completed the Social Responsiveness Scale. Symptom severity was assessed using the Autism Diagnostic Observation Schedule (ADOS). Results indicated that parent and teacher ratings were statistically significantly correlated at the beginning and end of the academic year, but only for severely affected children. Teacher report of social deficits was correlated with symptom severity as measured by the ADOS; parent report was not. These findings have implications for improving assessment procedures and parent-teacher collaboration.