In Irish classrooms, one option for educating children with Autism Spectrum Disorder (ASD) involves placement in a special class co-located in a mainstream primary school. This study surveyed 125 primary school teachers who taught in these classes. An evaluative framework of teachers' professional development was used to analyse primary teachers' perceptions of the special class model of provision and the teaching practices that they used. While teachers experienced challenges in these settings that included managing challenging behaviour, perceptions of the special class model were positive. Inclusion of students from special classes to classes in the mainstream context was limited for pupils with greater needs. A wide disparity in the delivery of the curriculum taught in these settings was also identified. Results revealed the need for professional development programmes for teachers to alleviate their experiences of stress and isolation and to improve the outcome of children with ASD.