Collaborating with Head Start programs in Waltham and Boston, Massachusetts, the researchers are implementing and assessing the Program-Delivered Literacy Through Inservice Training (PD-LIT) to work with Head Start programs to create systems that include in-service training, supervision, and program self-evaluation that enable programs to support children's language and literacy development. PD-LIT has three goals: (1) deepen knowledge of language and literacy among all center staff, (2) develop a center-wide shared vision of good practice; and (3) enhance children's language and literacy development significantly. PD-LIT is a two-year intervention that includes literacy concepts and practices workshops, professional conversations and demonstration classrooms, and supervisory methods to ensure valued practices are implemented. Researchers will train Head Start staff to become PD-LIT mentors and deliver training to their own staff. Using HLM, the researchers are examining the impact of PD-LIT on English- and Spanish-speaking children, comparing fall-to-spring change scores in children in PD-LIT classrooms to fall-to-spring change scores of comparison group children. The comparison group data were collected using the same tools and procedures as for PD-LIT. In Phase III a qualitative study will assess the stability and impact of PD-LIT. The researchers are studying PD-LIT replicability using a random assignment design, and are also conducting a process evaluation throughout the study period.