This qualitative research examines the question: In what ways does a developmental evaluation of a STEM program co-developed through a design thinking process illuminate program goal attainment? Students, parents, teachers, high school staff, school district administrators, advisory committee members, community, and college and university partners in a southern Ontario region participated in a collective effort to develop an innovative approach to STEM education in the context of the United Nations' Sustainable Development Goals, collaboratively prototyping the concept in a design workshop, and further refining it with diverse stakeholders. Collaborators co-constructed a developmental evaluation framework to continuously learn from experimentation toward program goals. Data sources include participant observation, field notes, interviews, and document analysis. Findings highlight program strengths needed to sustain it, and challenges that threaten its longevity. The paper concludes with a program assessment based on its intended impacts and opportunities to scale a design thinking approach in education to other jurisdictions.