ABSTRACT This article details and reflects on an action research project that explored the in-class wellbeing of children with autism within a mainstream primary school in Wales. It also sets out why reflective practice alone may be insufficient in the process of achieving positive change. Through the iterative reflective cycles of action research, drivers that promoted positive wellbeing in children with additional learning needs were identified, and barriers to these children’s happiness were confronted. Driven by a commitment to effective inclusion of all learners, the initial reconnaissance phase of the research recorded that episodes of in-class low wellbeing experienced by children with autism were higher than those of their fellow classmates in terms of their frequency and severity. This discovery inspired a collaborative process of pedagogic inquiry to find positive change. Teachers working across year groups developed, trialled, and reflected on interventions that aimed to improve the daily lived experiences of children with additional learning needs and enhance educational outcomes. The exponential growth of children identified as having autism makes research into the in-school positive wellbeing of this group both necessary and urgent. It is hoped that this study will inspire others, both in school and in wider contexts, to undertake action research to improve the lives of children with additional learning needs, such as autism.