This project undertakes a four-year research and development effort to produce a comprehensive, conceptually-based physics program that integrates video-based, inquiry-based, and lab-oriented materials with findings from current research in preconceptions along with an effective pedagogy for use in physics teacher enhancement workshops. In the initial stage an Oversight Committee composed of physicists, researchers, and other experts will be established to examine existing materials, such as PRISMS, CASTLE, InfoMall, Physics Teach to Learn, and Mechanical Universe, in light of research findings in physics education. The goal will be to assemble "best of the best" into a coherent, multi-faceted Core Curriculum materials for teachers of physics and to produce a Workbook for student use. All the materials will take an approach focussed on identifying students' preconceptions and misconceptions and replacing them with sound concepts. An Academic Council of high school teachers will develop a draft of the comprehensive program in the first year of the project for review by the Oversight Committee. The Project Staff will then refine the materials. In the second year of the project, the Core Curriculum will be used for the education of seventy-five Leaders of Physics Instruction (LPIs) through a four-week long summer Leadership Institute at the University of Dallas. During this Institute the LPIs will explore the materials and their effective use, gain insights into teaching through a conceptual approach, and have the opportunity to teach certain concepts to their peers. During the following academic year, these teachers will use the materials in their classrooms and evaluate their effectiveness for improving students' understanding of physical concepts. In the third year of the project, the LPIs will offer workshops for less-prepared physics teachers in their regions. Local Educational Agencies will contribute to the project through the purchase of the materials for their teachers. In the fourth year of the project, the LPIs will have a follow-up session to assess the workshops and to make plans for continuation of the program beyond the period of NSF support. Through the continued offering of workshops by LPIs, that will be supported by non-NSF funds, it is estimated that 750 teachers and 30,000 students per year will be impacted by the project. Cost-Sharing equals 100% of the NSF award.