Dr. Susan Jo Russell began her career in education as a K–3 classroom teacher and elementary mathematics coach. For the last four decades, she has been a senior researcher at TERC, where she spearheaded the original development and second edition of the K–5 mathematics curriculum, Investigations in Number, Data and Space, and co-authored many publications, including the Developing Mathematical Ideas professional development series and But Why Does It Work? Mathematical Argument in the Elementary Grades. She contributed to the launching of the Forum for Equity in Elementary Mathematics (https://www.terc.edu/mathequityforum/).

 Dr. Deborah Schifter has worked as an applied mathematician; has taught elementary, secondary, and college level mathematics; and, since 1985, has been a mathematics teacher educator and educational researcher at Mount Holyoke College and at the Education Development Center. She has authored or co-authored numerous publications, including: Reconstructing Mathematics Education: Stories of Teachers Meeting the Challenge of Reform; the professional development series, Developing Mathematical Ideas; a two-volume anthology of teachers’ writing, What’s Happening in Math Class; and But Why Does It Work? Mathematical Argument in the Elementary Grades.