Adaptive functioning of autistic children is traditionally measured through informant-report, often from parents. Behaviour varies across settings though, and context-specific reports should be considered. Limited and inconsistent results show low parent-education professional concordance, but no research has yet explored item level response variation. We investigated Vineland Adaptive Behaviour Scales-II concordance using 233 lower ability autistic children from the PACT-G sample. Domain and item level agreement was low, but better on objectively measured behaviours. Higher child nonverbal ability improved concordance. Where disagreements occurred, education professionals identified emergent skills more and parents were more likely to rate present/absent. Parents and education professionals view the adaptive abilities of autistic children differently and both should be considered when developing personalised interventions and support.