Interventions based on applied behaviour analysis (ABA) have been shown to improve outcomes for young children with autism spectrum disorder (ASD), but there is very little research into outcomes for older pupils. This study evaluated the effectiveness of an ABA intervention for pupils with ASD and additional learning difficulties in a UK special needs school. The aim of the intervention was to reduce barriers to learning for individuals aged four to 13 years old. Behaviour analysts collaborated with school-based teaching teams to design and implement function-based behaviour support plans, individual education programmes and ABA teaching strategies, and to promote the generalisation of skills. Pupils were assessed at baseline and again following one academic year of intervention. The pupils demonstrated significant gains in learning skills, language and communication, social and play skills and self-help skills. Pupils of all ages acquired essential 'learning to learn' skills which have reduced their barriers to learning and are enabling them to learn more effectively. The article discusses how a behavioural model was successfully and affordably implemented across key stages within a special educational needs school.