This five-year prevention services application is concerned with preventing substance abuse, comorbid mental and behavioral disorders, and school failure. We will direct an integrated set of first grade classroom based preventive interventions at two correlated and confirmed early antecedents: early aggressive, disruptive behavior and poor achievement. We will test a comprehensive Whole Day (WD) program directed at improving: 1) teacher's classroom behavior management; 2) family/classroom partnerships regarding homework and discipline; and 3) teacher's instructional practices regarding academic subjects, particularly reading. We will test WD effectiveness in a developmental epidemiological design in which children and teachers are randomly assigned to intervention and standard setting (control) classrooms in 2 classrooms in each of 12 schools. While following the first grade children to the end of third grade, we will follow their first grade teachers over two subsequent cohorts of first graders to test whether the support and training structure sustains high levels of WD practice. We will also test whether the support and training structure is successful in training non-WD teachers. This prevention services aim will be augmented by an economic analysis of the costs and cost-effectiveness of the WD program. This combined services and prevention research should increase the efficiency of developing evidence-based programs and extending their use system-wide in both the prevention and education fields. The aims of our proposed work are to: 1) Implement and evaluate the effectiveness of a whole-day preventive intervention program for first-grade (WD) directed at known antecedent risk factors for later substance abuse, school failure, and comorbid mental and behavioral disorders; 2) Measure the variation in impact of WD due to variation in the experimentally manipulated quality of teachers' specific WD practices around classroom behavior management, family/classroom partnership, and quality of instruction, regarding reading, taking into account family, peer, and community factors; 3) Test effective- ness of the support structure required to sustain, and extend to other teachers high quality implementa- tion of WD; 4) Carry out economic analyses of the costs of implementing WD and their cost-effectiveness.