To determine the relative effectiveness of different methods of preschool educational intervention for disadvantaged children, comparisons were made of five programs whose levels of structure ranged from the traditional nursery school to a highly structured preschool. Subjects were 79 4-year-olds representing a wide range of ability levels. Intervention effects were evaluated at the end of the preschool year and also, at the end of the kindergarten year. Follow-up data were collected at the end of first grade for three of the programs. Preliminary results were differential and encouraging for the more structured programs. The ameliorative preschool provided a framework for the subsequent investigation of related variables: effects of initiating the program with 3-year-old, low IQ children, and the feasibility of using paraprofessional staff as teachers. Included in this report are studies undertaken to provide instructional programs for children under 3 years and to find techniques to train mothers in home intervention. (MS)