To broaden participation in high school computer science (CS), we launched a four-year researcher-practitioner partnership (RPP) with Massachusetts schools starting in September 2021. Through this initiative, we facilitated recurring virtual sessions with cross-functional teams of educators—including teachers, guidance counselors, and administrators, who collaborated to design, implement, and refine action plans aimed at increasing access and equity in CS education. By the third year of the program, participating schools had developed tailored strategies, created progress-tracking tools, and shared implementation resources within and across districts. This experience report draws on lessons from the third year to highlight what works, and what doesn’t, when supporting schools in broadening participation in computing (BPC). First, we found that cross-functional educator teams generate a multiplier effect: collective efforts led to more sustainable and impactful change than isolated individual actions. Second, we observed that underestimating the time and personnel commitment required can lead to participant attrition and limit success; intentional planning and administrative buy-in are essential. Third, while RPPs like this serve as meaningful catalysts for local change, we argue that systemic shifts, such as implementing a statewide high school CS graduation requirement, would dramatically expand participation and opportunity in a shorter time frame. Our findings offer insights for researchers, policymakers, and educators aiming to scale equitable CS programs and sustain progress beyond isolated interventions. We share key artifacts, frameworks, and recommendations to guide similar initiatives and support long-term systems change in CS education.

Keywords: Computer Science Education, Cross-Functional Teams, Counselors, Teachers, Administrators, Researcher-practitioner partnerships.