This study addresses the process of developmental change as it occurs in the course of classroom lessons. The book aims to answer such questions as what forms of teacher-student interaction are most effective for producing developmental transformations in children's understanding. It also addresses why knowledge derived from psychological experiments on children's learning and development so often seems irrelevant to classroom teachers and how it is possible to reconcile Piaget's emphasis on the central role of independent intervention and constructive activity with learning theorists' emphasis on environmental feedback as the motive force of change. Assuming that intellectual development occurs in the "construction zone," a shared space encompassing the joint constructive efforts of teachers and students, the authors provide innovative answers to these and related questions. The questions are illustrated with detailed analyses of specially constructed lessons in the instructional areas of natural science, social studies, and mathematics.