The authors supervised and trained pre-service teachers while conducting extended school year (ESY) services for pre-kindergarten and elementary students with autism spectrum disorder (ASD) and other developmental disabilities (DD). Each classroom was responsible for conducting communication assessments and developing interventions focused on increasing functional communication. One intervention, the Picture Exchange Communication System (PECS™), was taught to three pre-service teachers and staff who implemented PECS™ with four students who lacked functional communication skills. The teachers were mentored as they implemented the appropriate level of PECS™ and developed communication books for the students to use in school, home, and other settings.