Argues that scientific knowledge in school is a social construct in which curriculum proposals are simply points of departure that are transformed by the social interaction that takes place within the classroom. Considers discourse as playing an important role in knowledge construction. Contains 31 references. (DDR)

Illustrates the construction of conceptual models on pressure and flotation using high school students' previous ideas on these concepts. Identifies three models and uses them to analyze students' ideas about physical phenomena and to recognize the inferential structure they use. Contains 28 references. (DDR)