This study examined cognitive and affective development among children in ten preschool (Head Start) programs in the Boston area that varied in socioeconomic class, racial composition, and cultural emphasis. Data, collected over a two-year period, were compared in an effort to ascertain the effects of socioeconomic status and racism on the children. In three of the schools a self concept training component was introduced. The main focus of this component was to test selected training techniques and materials with parents, teachers and social workers for effectiveness in building self esteem among black children. The Boehm Test of Basic Concepts, the Scamin Self Concept and Motivation Inventory, and a school observation form were used to measure cognitive and self esteem. Results indicated that: (1) racial mixing appeared to have negative consequences for cognitive development among black and white preschool children when the school's cultural emphasis was white, but not when the emphasis was black; (2) middle class children in racially mixed groupings showed superior mastery of conceptual knowledge in schools whose cultural emphasis was white, but not in those whose emphasis was black; and (3) the self concept training component appeared to be successful. A copy of the school observation questionnaire is included among the appendices. (ED)