(Orginally published in 2005) This monograph represents the work of many mathematics teacher educators explored the content knowledge and pedagogical knowledge that make up the middle grades learning experience. The middle grades remains a unique period of time in students' development and as such provides both challenges and promising opportunities for those who prepare teachers of middle grades mathematics. This work is the final product of an exciting NSF supported endeavor that gathered leaders in the field and explored curriculum, case studies of program models at several institutions, as well as issue papers on such key topics as assessment, technology, and preparing culturally responsive teachers. AMTE hopes this monograph will stimulate discussion and bring attention to this critical period of schooling.