This study examines teacher learning from the perspective of cultural–historical activity theory, which emphasizes the creation of new environments and new artefacts. This study focuses on elementary school teachers' learning over the course of professional development (PD) sessions for equitable mathematics teaching. Within the PD, the teachers created a student project that investigated linguistic diversity in the school community. Thematic analysis reveals that teachers' discourse relating to teaching mathematics to English language learners (ELLs) changed after the implementation of the inquiry project. More specifically, the discourse shifted from focusing on ELLs' barriers and challenges to highlighting what ELLs can do. This shift was coupled with a change in the classroom mathematics learning environment.