The social context of a classroom is actively created by teachers and learners. Instead of looking at the context as the background for cognitive work, we might look at it as an externalization of cognitive work. The teacher creates a social system in the classroom that supports certain kinds of discourse and activities; students collaborate within the system, contributing observations, answers, and concrete products such as text, projects, and data. The cognitive system includes the externalized tools, texts, data, and discourse all of which is produced by and for the activities. This takes us a step away from traditional psychological approaches that look at the individual mind as the basic unit of analysis. Studying the interactional system, reveals unique properties that support cognitive change. This research perspective then provides another way to look at the design of technology to support interactional systems that are productive of change.