At the heart of many STEM ecosystem models are cross-sector partnerships between formal K-12 education and informal learning agents. Informal/formal education cross sector partnerships are considered effective models in enriching STEM education for youth underrepresented in the STEM disciplines. In this paper, we identify benefits of a cross sector partnership from the point of view of the staff, youth participants, educators, and leadership engaged in the partnership. We focus on explicit, intended youth outcomes–engaging young women of color in engineering to support their career aspirations in the fields–as well as emergent themes, primarily noted by formal educators and formal education leadership, regarding the mechanisms by which partnership with a non-profit has influence students, teachers, and the school community. Evidence indicates the design of the partnership allowed for each party to share practices, material and human resources that minimized duplication of efforts of stakeholders. The study also shows how by integrating an afterschool program into the school community, Techbridge Girls creates opportunity for informal and formal settings to reinforce one another in ways that are less common in traditional, stand-alone informal STEM learning.