Many education reformers criticize the mediocre state of learning in high schools in the United States. In order to insure that all students have equal access to high quality teaching, it is argued that educators must explore the potent connections among school setting, ability grouping, teaching methods, and student opportunity to learn. The research described in this paper analyzes student opportunity to learn U.S. history in 6 schools and 24 classrooms across various ability groups. The goal study's was to determine whether inequitable opportunity to learn exists within a varied sample of high school U.S. history classrooms, and to discern whether such differences can be explained by school level characteristics, teacher characteristics, and the ability group structure. The paper presents a conceptual framework and literature review; study design and sample; the opportunity structure established by school policy regarding ability grouping, class size, and curriculum/tests utilized; the degree of engagement instruction; school, teacher and ability group differences in the opportunity offered by instruction; and summary of school, teacher and ability group influences on student opportunity to learn. A number of complex interrelationships among school, teacher, and ability groups influences are observed. For example, questions concerning the equitable distribution of opportunity to learn U.S. history and critical skills such as discussion and writing are raised. Differences in teacher pedagogic skills, such as classroom organization and management, clearly influence student opportunity to learn. A number of figures and tables are included as is a 35-item bibliography. (DB)