The Picture Exchange Communication System (PECS) is an Augmentative and Alternative Communication (AAC) system which is widely used to support children with developmental disabilities. In the present study, we surveyed individuals responsible for implementing PECS in special educational settings in the United Kingdom (N=283). We explored knowledge of and adherence to the intervention, with a view to identifying training and support needs. Specifically, we examined participants' knowledge, implementation accuracy, training experiences, access to resources, and attitudes towards PECS. We developed hierarchical logistic regression models to explore the association between training experience and both knowledge and use of PECS. We pre-registered our methods, predictions and the analysis plan on the Open Science Framework (OSF).We found considerable variation in practitioner knowledge and implementation of PECS. Formal training predicted greater knowledge and more accurate implementation when practitioner role and the degree of setting support were accounted for. While PECS was rated by a large majority to be effective and practical, many participants identified that time and the availability of resources were barriers to implementation. We also found that the purpose of PECS was not always fully understood by practitioners, and we identified some consistent gaps in knowledge and implementation. This study contributes new information regarding the real-world use of PECS in educational settings and offers new insights for supporting practitioners.