This current study draws on data from a large sample of trainee teachers in England to provide a long overdue baseline assessment of the knowledge of autism. It has particular import given the recent research that shows that 60% of autistic young people identified ‘having a teacher who understands autism’ as the main thing that would make school better for them. We find that, based on the Autism Awareness Survey, levels of knowledge were comparatively high among our n = 326 respondents. However, whilst this is encouraging, our findings also point to an underestimation of knowledge, which indicates the need for additional resources and training to develop trainee teachers’ self-efficacy and confidence in their pedagogical practice. Finally, in order to understand more about the gap between autistic children’s experiences and teachers’ understanding, this study signals a need to review autism knowledge scales to better reflect an experiential knowledge that goes beyond the clinical descriptors.