We have discovered a new and formerly unstudied long-term impact of a system-wide research university program that provides opportunities for students to explore secondary school teaching as a potential career. Looking beyond teacher recruitment as the only assessment of success, we have investigated the impact of the program on those who explored teaching but chose not to enter that profession. Our study surveyed students who had participated over a 10-year period in our California Teach courses, which integrate evidence-based, best-practices of pedagogy, internship, and reflection. Among our results we have found that well-crafted service-learning courses for STEM (science, technology, engineering, and mathematics) majors, which include internships in K-12 schools, create positive and lasting changes in attitudes toward public school teachers, in interest in future volunteering in public schools and in intentions to support outreach efforts in the workplace. Improving public opinion of the value of STEM teachers and public education can only bode well for the future of science teaching and the overall science workforce.