The majority of children and young people with autism spectrum disorder are educated in mainstream schools. The diverse needs of this group of pupils has led to a continuum of provision being promoted in the UK and other countries, and developed at a local level. This continuum includes mainstream schools with resource provision which can offer enhanced physical and staffing resources beyond those normally provided in mainstream schools. How teaching staff perceive such provisions and their development over time have not previously been investigated. The current study was designed to explore the perceptions of staff working in five primary and three secondary school resource provisions in one local authority throughout the first year of the provisions and at three-year follow-up.Sixty-six interviews with senior teachers, mainstream teachers and resource provision staff took place during the initial year, with 21 three-year follow-up interviews. Data were analysed using inductive and deductive thematic analysis. Data provide tentative support for Bronfenbrenner's bio-ecosystemic theory as a framework for representing the complex interactions within the resource provision schools, between systems and their development over time. Findings and implications are discussed in relation to theory and practice.