Core diagnostic features of autism include deficits in social-communicative functioning. Two pivotal skills for young children with autism include joint attention and pretend play, which constitute early foundations upon which later social-communicative skills are built. Joint attention (characterized by behaviors such as pointing, showing, and coordinated looking to share attention toward objects or events with another person) and symbolic play (characterized by the ability to pretend), play important roles in language development and social engagement with peers. Children with autism show deficits in these skills. Advancing Social-Communication and Play (ASAP) is an intervention that has recently been developed to help preschool children with autism learn and practice these important skills. The purpose of this research is to conduct a cluster randomized trial to evaluate the efficacy of ASAP. The major goals of the project include investigating whether children experiencing the intervention, when compared to those who do not, demonstrate greater gains in the proximal child outcomes of social-communication and play skills as well as the more distal outcomes of language development and engagement with classroom objects and peers. The study will also examine whether child-level (i.e., developmental level, problem behaviors) and teacher-level (i.e., teacher burnout, general classroom quality) characteristics moderate the impact of the intervention, and whether the level of implementation fidelity mediates its impact on child outcomes. For each cohort, classrooms are randomly assigned to the ASAP or control group. Baseline (pre-test) data will be collected on all child and teacher/classroom measures. For the treatment group, coaches (trained by ASAP staff) at each of the four study sites will train and provide ongoing support for the local educational teams implementing the intervention. For the duration of the school year, the treatment group will experience the ASAP intervention, which includes group activities and one-to-one teaching sessions on social-communication and play skills, and the control group will experience business-as-usual conditions. At three additional points in time, including during the post-test at the end of the year, the investigators will collect data on the social-communication and play skills of all children. At the end of each school year, the investigators will also collect post-treatment data on child language and engagement skills. Intervention fidelity will be measured in all classrooms several times each year. Products from this project will include published reports and presentations on the efficacy of the ASAP intervention.