Frameworks that seek to understand how knowledge restructuring occurs and how to build a learning environment that facilitates this restructuring raise important philosophical, psychological and pedagogical questions and issues about how conceptual change occurs and what characteristics of knowledge growth ought to be a part of curricula and learning environments. Implicit in emphasizing the how is a shift in science educations' perspective from one that embraces “scientists' ways of knowing” as the dominant objective towards one that favors “positioning the learner for the next step.” This change in perspective and approach represents a radical and complex departure from common practice. This article advances a piecemeal model of the character and mechanism of restructuring and then describes a model of educational practice designed to facilitate this form of restructuring. We argue that a piecemeal developmental perspective of conceptual change would offer quite different criteria for deciding what to teach and how to teach. The adoption of conceptual change teaching models implies teacher empowerment of a kind we have yet to fully understand. Empowering teachers with appropriate philosophical and psychological models for the selection and the sequencing of instructional tasks would aid in their describing and prescribing effective or meaningful learning strategies. Central to this educational model is a broadened and integrated view of assessment and instruction that we are calling a portfolio culture. The essential characteristic of this culture is that it creates opportunities for teachers and students to confront and develop their scientific understanding and to equip students with the tools necessary to take increased responsibility for their own restructuring, to assess for themselves what might be the next steps.