This action research sought to evaluate the effect of peer teaching structures across subgroups of students differentiated by language and mathematical skill ability. These structures were implemented in an effort to maintain mathematical rigor while building my students' academic language capacity. More specifically, the study investigated peer teaching's influence on mathematical flexibility, reasoning, and math mastery over time. Students across all subgroups grew significantly in the flexibility and efficacy with which they applied strategies in math. While growth in academic vocabulary integration and process writing was not as strong, students with lower math or limited English language abilities showed meaningful qualitative growth in their ability to take risks, share their reasoning, and respond to the thinking of others.