Colleen Oppenzato’s research focuses on how students develop mathematical thinking, from early childhood through the middle grades. Her specific interests include children’s understanding of rational numbers, how textbook input affects student learning, and how to measure teachers’ math pedagogical content knowledge. She is currently completing her PhD in cognitive science in education at Teachers College. Prior to joining NWEA, Colleen worked as an elementary school and middle school special education teacher and then as a math curriculum developer, editor, and project manager. She was also an affiliate with the Development and Research in Early Math Education (DREME) Network, where she created materials for teacher educators and for family math activities.