Rates of children identified as having autism spectrum disorder (ASD) continue to increase in both medical and school settings. While procedures for providing a medical diagnosis are relatively consistent throughout the United States, the process for determining special education eligibility under an ASD classification varies by state, with many states adopting looser identification criteria than medical taxonomies. This study included a sample of 73 school-age children with ASD and sought to examine differences in ASD symptom severity, adaptive functioning, and challenging behaviors between those identified in the medical system versus those identified in schools. Results indicate that children identified as having ASD only by their school had less severe clinician-rated ASD symptomatology than children with a medical ASD diagnosis but that caregiver reports of adaptive functioning and challenging behavior did not differ between the two groups. These findings do not appear to have been influenced by demographic factors including caregiver education, household income, or health insurance status. Implications and directions for future research are discussed.