The overall aim of this article is to analyse how a school's special needs unit in Sweden deals with children's agency and category work as they negotiate and categorise the problems that are encountered there. The data derive from an ethnographic study conducted in a Swedish special educational needs unit (SENU) attended by a group of five boys aged between 7 and 12. The results show that the teachers' categorisations of the boys' emotional and behaviour problems and attention-deficit/hyperactivity disorder (ADHD) could be interpreted as an attempt to guide the boys' development so that they will change and improve. Conversely, from the boys' perspectives, the daily activities in the SENU could themselves be problematic in that the boys are obliged to adopt several different strategies to control and strengthen their identity. These observations highlight the importance of detailed analyses of the boys' communicative activities during their interactions with teachers and peers.