9731064 Shifter ABSTRACT: This project entitled, Teaching to the Big Ideas of Geometry, Measurement and Data Analysis involves the creation of professional development materials which are designed to help teachers of K-8 mathematics understand the mathematics they teach, understand how children learn this material, and ultimately, improve their mathematics teaching. The project is directed by Deborah Schifter of the Education Development Center (EDC), with Co-PI's Susan Jo Russell of TERC, and Virginia Bastable of Mt. Holyoke College. This is a 4.5 year project, which will involve between 540-640 teachers. This project builds off of a prior funded project that dealt with Teaching to the Big Ideas involving number. Within each project module proposed in this project, the writers plan to integrate a variety of activities centered around print and video cases. This will include mathematics examples, investigation of the thinking of students, an analysis of tasks drawn from NSF-funded elementary curriculum projects (Investigations, Trailblazers, and Everyday Math), and the reading and review of research related to a theme central to the module. The PI's believe strongly that teachers can improve aspects of their teaching practice through engaging discussions with their peers. Cases situated in a classroom context help to provide the access to the issues driving such discussions. All of the NSF-funded elementary curriculum projects will be used in this project as the source of mathematics tasks.