This article examines the mathematics learning experiences in proportional reasoning I created for pre-service teachers in my teacher education course in Canada. The approach aimed to enable pre-service teachers to work on and with their prior mathematics understandings, make connections that were particular to what emerged during group work, and practice co-teaching. I describe the details of these experiences, so other educators might be inspired to explore similar mathematics learning with their students, including in upper primary and lower secondary classrooms, when transitioning from additive to multiplicative thinking.