Current literature reports that the reorganization of schools through national efforts is not closely paralleled to subsequent local classroom changes. The focus of this study concerns teachers' beliefs and their interpretations of a 2-week summer institute intended to change their treatment of scientific knowledge and assessment strategies at the classroom level. Furthermore, this study suggests that major contextual barriers to change should be identified and support should be provided to help teachers interpret and rethink their practice in venues beyond institutes. Despite collaborative efforts, participants were found to maintain their entry level fundamental beliefs about the nature of scientific content knowledge, teaching, and assessment practices. Reaching beyond past research on reform and reports of change in teachers, this study attempts to explicate the struggle of making lasting and deeply rooted change in teacher beliefs that results in the transformation of traditional science teaching. © 1997 John Wiley & Sons, Inc. Sci Ed 81:137–159, 1997.