The research question of this project asks whether intensive training in, and confirmed practice of, a proven curriculum model enables Head Start teachers to contribute significantly to children's development, especially their development of language, literacy, and the ability to resolve social conflict. It also asks the related question of whether Head Start teachers who claim to use a proven curriculum but have little or no training in it, and have not confirmed their practice of it contribute significantly to children's development. The proposed project will use a curriculum model of proven effectiveness, the High/Scope curriculum framework, to test this hypothesis. The intervention we propose involves intensive curriculum training and curriculum implementation confirmed by systematic observation. We ask if meeting these conditions contributes significantly to children's development. The primary intervention will involve 20 Head Start classrooms of Oakland Livingston Human Services Agency. From March to August 2001, we will plan and provide 30 days of training, observation-feedback, and discussion for the teaching staff, collecting curriculum data quite regularly. We will track their classroom program for two years, collecting observational data on children regularly throughout. We will identify a second Head Start agency for the secondary intervention, randomly assigning 20 classrooms to a comparison group and 20 classrooms to the intervention group, which will receive 30 days of training, observation-feedback, and discussion during the 2002-2003 program year. We will track their classroom programs for two years, following the same data collection schedule as before for both groups. Today's key challenge to Head Start is to identify program practices that contribute to program effectiveness. The High/Scope curriculum model is one of the few interventions with evidence that it serves this purpose. We propose to test the effectiveness not of this proven curriculum model, but rather of intensive training in this validated curriculum model and its verified implementation in Head Start. In this way we will determine whether the tougher curriculum standards we propose - validated curriculum model, intensive curriculum training, and verified implementation - are critical to Head Start's success.