Access to science, technology, engineering, and mathematics fields serves as a key entry point to economic mobility and civic enfranchisement. Such access must take seriously the intellectual power of the knowledge and practices of non-dominant youth. In our case, this has meant to shift epistemic authority in mathematics from academic institutions to young people themselves. This article is about why high school-aged students, from underrepresented groups, choose to participate in an out-of-school time program in which they teach younger children in the domains of mathematics and computer science. It argues for programmatic principles based on access, identity engagement, relationship building, and connections to community to support underrepresented youth as learners, teachers, leaders, and organizers in mathematics-related activities using game design as the focus of activity.