This paper draws on a study of curriculum consonance (correspondence between teachers' goals, what ensues in the classroom, and what students learn) in three tenth-grade social studies classrooms. The three teachers had about the same number of years of teaching experience and educational attainment, and they were about the same age. The classrooms were observed for four weeks in each case, and descriptions and impressions of classroom life were recorded. Informal interviews were also held with the students. Three major places in the curriculum where consonance was jeopardized were identfied. In one case, consonance was lost within the intended curriculum--the aims held by two of the teachers were inconsistent with their specific curriculum plans. Consonance was also jeopardized in the translation of intentions into classroom events. A third source of dissonance in the three classrooms was conflict between the explicit and implicit curricula. These factors are analyzed and a discussion is presented on the implications of the findings for educational evaluation, teacher supervision, and curriculum decision making. (JD)