We aimed to explore the experiences of teachers, autistic students and students' parents, before and after professional development intervention for teachers in primary school. The main participants were five autistic students aged 7-11 years in three primary schools (intervention schools), their parents and teachers. Five school contexts were studied, with three interventions and two comparisons. Data collected included questionnaires, student evaluations and recorded follow-up conversations. The results showed statistically significant changes among teachers pre- to postintervention at all three intervention schools; no differences were found at control schools. However, analyses of the case studies showed that parents and students did not experience changes at the same levels as teachers. Identified barriers to change included a lack of physical space, time to focus on each child, and resources. Professional development is effective in changing teachers' understanding and attitudes, but not enough to change classroom practice in the views of students and parents.