LAUSR

Functional abilities in children with autism spectrum disorder (ASD) are highly heterogenous, and impairments can overlap with non‐ASD neurodevelopmental disorders. We compared the profiles of children assessed for ASD with and without an ASD diagnosis using a retrospective cohort study of 101,739 children born in British Columbia (2000–2008). The children were grouped into the following five comparison groups: (1) ASD− (n = 1131), (2) ASD+ (n = 1583), (3) Ministry of Education designated ASD+ (n = 654), (4) special need other than ASD (n = 11,663), and (5) typically developing (n = 86,708). Five developmental domains were assessed using the Early Development Instrument. ANCOVA was used to control for covariates, Tukey's HSD test for multiple comparisons, and Cohen's d for effect size. The ASD− group had slightly higher scores than the ASD+ group with small to medium effect sizes in all domains (d = 0.20–0.48). The ASD− group had slightly higher scores than the Ministry of Education ASD+ group in only three domains with small effect sizes (d = 0.21–0.25). The ASD− group had lower scores in all domains compared to the typically developing group with large effect sizes in all domains (d = 1.12–1.77). The ASD− group received less education funding at school entry than both ASD+ groups. Overall, only small to medium differences in development were detected between the ASD− and ASD+ groups. While these children differ diagnostically, they share similar functional profiles and have substantially more difficulties than typically developing children. Therefore, differences in levels of support at school entry raise critical questions of equity.