Is the quality of instruction systematically better in one subject than another? Teachers and students in the same Chicago high schools reported on one core-curriculum class (English, mathematics, science, or social studies) in 2007 surveys. Teachers commented on instructional demands and student participation. Students described engagement, academic demand, and clarity. Both described social relations. Using hierarchical linear models (HLM), findings across several diverse instructional measures were consistent by source (teachers or students). Respondents rated the quality of instruction lower in mathematics and science classes than in English and social studies classes. Students' instructional experiences seemed fragmented and inconsistent. Even in the same schools, teachers' descriptions of instruction differed by departmental affiliation. We draw policy implications from these instructional differences. (Contains 4 tables and 11 notes.)