The medicalisation of the behaviour of children is a phenomenon that is attracting growing attention, with particular concern about the increased likelihood of children living in disadvantaged contexts receiving a medical diagnosis, such as attention-deficit hyperactivity disorder, and treatment. This paper reports on a study of professionals involved with children experiencing behavioural problems. The professionals interviewed in this study articulated their own reservations about the medicalisation of children's behaviour and revealed a number of strategies for interrupting the process towards diagnosis. These interruptions, analysed using Deleuze and Guattari's concept of deterriorialisation, took place along linguistic, visual and affective planes and were successful in encouraging teachers and head teachers to see alternatives to the medical route. The findings have implications for existing practice in the response to, and support for, behavioural problems and for teacher education.