This report presents findings from a systematic review commissioned by the Department for Education as part of the What Works in SEND programme. The review examines the effectiveness, cost-effectiveness, and stakeholder experiences of specialist unit or class-based provision within mainstream schools. Internationally, a wide range of terminology is used (e.g. special units, resource bases and self-contained classrooms). Within England, equivalent provision has historically been described as SEN units or resourced provisions and, more recently within national policy, as inclusion bases. Throughout this report we use the term specialist unit/ class provision as an umbrella term encompassing these different models.
This is an international systematic review, drawing on evidence from multiple countries where terminology, structure, and organisation of provision vary considerably. Provision was included where it met the review’s operational definition of specialist unit/class provision within mainstream schools, namely designated specialist units or classes located within mainstream schools, designed specifically for children and young people with SEND, in which specialist staff delivered teaching and pupils typically spent a substantial proportion of their school time, regardless of how provision was commissioned or labelled within different education systems (see Section 3.3.1 for the full operational definition and eligibility criteria).
The review is situated within a context of significant reform and pressure within the SEND system in England. Policy developments, including the SEND Reform consultation (Department for Education, 2026d) and the Schools White Paper (Department for Education, 2026b), position specialist provision within mainstream schools (referred to in current English policy as inclusion bases) as one approach to supporting outcomes for children and young people with SEND, alongside wider system reforms. It is important to note that this review is not designed as a guide to the implementation of inclusion bases within the English system. Rather, it synthesises international evidence on comparable models of provision to inform understanding of how such provision operates and where evidence is currently limited. At the same time, there is limited consolidated evidence on how such provision operates, for whom it is effective, and under what conditions. This review addresses this gap by synthesising international evidence on specialist unit/class provision, with the aim of informing policy discussions, practice considerations, and priorities for future research. The review focuses on three key questions:
- What is the evidence on the effectiveness of specialist unit/class provisions in mainstream schools?
- What are the experiences of children, families, and professionals?
- What is known about costs and resource implications?