In the second session of the Forum for Equity in Elementary Mathematics Speaker Series, Dr. Susan Jo Russell and Dr. Deborah Schifter discussed a classroom practice that emphasizes mathematical discussion in which students build on each others’ ideas requires a dual commitment on the part of the teacher to deep mathematics and equitable participation. They viewed video from elementary classrooms in which teachers strive to enact this dual commitment while students dig into an investigation of arithmetic structure and considered how engaging with complex ideas can support equitable participation and how giving attention to a wide range of student ideas deepens the mathematics.