Teachers in residential special schools often work with young people who experience some of the greatest obstacles to learning. In particular, young people with profound and multiple learning difficulties (PMLD) and those with autistic spectrum disorders (ASD) require expert teaching and management by professionals who have a detailed understanding of the individuality of these young people. The identification of mental health difficulties in young people with PMLD or ASD is often confused by the challenge of interpreting behaviours which become associated with a “condition” rather than a manifestation of a mental health problem. This paper describes research which investigated professional understanding of and responses to mental health needs in young people with PMLD or ASD in a group of residential special schools. It is suggested that there remains a lack of understanding of the complex relationship between individual learning needs and mental health difficulties and that this is an obstacle to effective management and remediation. The development of greater cohesion across professional services and with families is perceived as an essential factor in enabling improved provision in this area