The academic progress and self-concept of North York (Ontario, Canada) learning-disabled and educable retarded students were studied, with particular reference to the effectiveness of placement in mixed exceptionality versus single exceptionality programs. Information was gathered from the published special education literature, students' files, pre-post assessment of changes in academic achievement and self-concept, and questionnaires administered to 28 parents and 78 teachers. Subjects involved in the study were aged 9-11, with 17 learning-disabled (LD) students in mixed exceptionality classes, 45 LD students in single exceptionality classes, 5 educable retarded (ER) students in mixed exceptionality classes, and 25 ER students in single exceptionality classes. Analysis showed that the LD pupils in single category classes fared best in terms of academic gains in reading, spelling, and arithmetic. No significant self-concept changes were found. Most parents were satisfied with their child's placement. Only modest differences were noted in teachers' views regarding effect of single and mixed exceptionality programs. Appendices contain a literature review, case studies of six students, copies of the parent and teacher questionnaires, and detailed data from the questionnaires. Includes 10 references. (JDD)