This study involves 25 inclusive preschool classrooms. The study uses an randomized controlled trial to estimate treatment impacts of a peer-mediated intervention, with 12 classrooms assigned to the treatment condition and 13 to the control condition. Within each classroom, the focal participants are children isolated from their classroom social network with low pragmatic language skills. One target child is selected per classroom using a priori exclusionary and inclusionary criteria. In the fall of each year, simple random assignment is used to allocate classrooms to the treatment group and to the control group. First, investigators identify all children's positions within the classroom social network using a teacher matrix conducted in fall of the academic year; from this network a child-level social network index is calculated (i.e., individual degree centrality; lower scores are characteristic of social exclusion). Second, teachers simultaneously complete the Developmental Pragmatic Profile (DPP) for each child in the classroom. Finally, among the participating focal children, investigators select the target child based on the lowest centrality scored weighted by DPP score, so that focal children represent the most socially isolated children with the poorest social-pragmatic communication skills. Children and teachers participate for a 9-month period, and the primary approach to treatment for focal children is described here. Specifically, focal children in classrooms randomized to the treatment condition receive peer-mediated pivotal response training (PRT) per procedures detailed by Brock et al.. PRT procedures are facilitated by a classroom facilitator-a classroom teacher or teaching assistant-who receives ongoing training and support from research staff.

First, investigators provide a one-on-one 1-h training session for each facilitator that focuses on how to identify, initially train, and then support peers on a day-to-day basis during center time. Second, investigators partner with the facilitator to identify two peers who (a) demonstrate good social skills; (b) respond well to adult directions; (c) have consistent attendance; and (d) do not have a history of negative interactions with the target student. The facilitator explicitly identifies the focal child ("buddy") and asks the children to use three strategies to play with the buddy during center time: (a) offer buddy some play options; (b) show and talk about how to play with buddy; (c) compliment buddy. At each training session the facilitator describes one strategy, provides examples, and has peers practice the strategy through role play. During the role play the facilitator encourages and coaches peers to use the strategy as intended. The facilitator then provides ongoing support to peers during center time to implement the strategies by helping peers to set goals immediately before center time for use of the strategies, regularly encouraging peers and supporting peers to use the strategies, praising peers for use of the strategies, and reviewing peers' goals and interactions with the focal child at the end of center time. Facilitators provide this support during center time at least three times weekly for a 12-week period. The investigators propose that improved socialization experiences in the preschool classroom for focal children can disrupt the social exclusion, leading to accelerated growth in linguistic, social, and behavioral outcomes.