This research was conducted by the Department for Education (DfE) to explore the models, uses and perceived outcomes of in-school support units within mainstream schools in England. Ten mainstream secondary schools across England, including 12 members of school staff, were interviewed by DfE social researchers to understand the purpose, use and outcomes associated with using in-school support units. As a small-scale qualitative study, with a low sample size, the findings only represent the views and practices of those who agreed to take part in the research and cannot be generalised wider.