Over 90% of students with complex support needs are taught in self-contained (segregated) special education classrooms for most of their school day, despite accumulating evidence these classrooms are not associated with positive student outcomes. Yet placement in these segregated classrooms persists, in part because of assumptions about the degree of specialized, intensive, and individualized instruction that occurs in these settings. We observed a national sample of 30 students with complex support needs using time sampling and fieldnote data in this convergent parallel mixed methods study to describe (a) the ecobehavioral characteristics of classrooms, (b) the learning activities occurring in classrooms, and (c) how the materials, supports, and learning activities explain student experiences in these classrooms. Quantitative time sampling data indicated that students experienced passive learning opportunities and downtime, with few occasions to engage with other peers or grade-aligned content. Qualitative fieldnote data provided context for the quantitative results. These findings provide a picture of the low expectations that persist in segregated classrooms and contradict the need to remove students from general education to learn in segregated classrooms.