Segregation has been part of the cultural design of American society from the pre-industrial rural period to the present, post-industrial urban period. This paper, however, is concerned with learning within contemporary school settings. Ethnic segregation is one major type of group separation within American schools and within the society. Socioeconomic status, age, sex, religion, and physical or mental exceptionality are among the principal other group distinctions used to segregate groups in American society. Each ramifies profoundly into the organization of American schools--public and nonpublic, lower and higher systems, alike. Correlatives which are also used to segregate students and staffs include region of origin, mother tongue, dialect, and even life style. Among all of these, perhaps the only categorical distinction to be given a stronger emphasis within schools than within the society is imputed mental ability. Our purpose is to understand students--the social and educational forces that influence their learning within the school context. Therefore we narrow our attention to the kinds of segregation which are carried into classrooms in American schools, and to the kinds of cognitive skills that are conventionally recorded as school learning. (Author/JM)