The prevalence of autism spectrum disorders (ASD) has risen dramatically in the past decade and children are being identified at earlier ages, putting pressure on school districts to provide effective interventions for these young children. One comprehensive treatment model that aims to address this need for effective early intervention is Project DATA (Developmentally Appropriate Treatment for Autism). This model blends practices from the fields of applied behavior analysis, early childhood education, and early childhood special education. The purpose of this research is to evaluate Project DATA for preschool children using a randomized controlled trial. The research team will examine the impact of the intervention on child cognition, language, social skills, and behavior. They will also investigate potential child-level moderators as well as family functioning and satisfaction as potential mediators of intervention effects. Twelve schools will participate, each with at least 10 children with clinical levels of ASD symptoms.