Gender stereotypes and lack of access to relatable role models, mentors, and STEM opportunities have
been suggested to deter middle school girls and students from underrepresented backgrounds away from STEM. Seeds of Success, an out-of-school program, is designed to inspire girls to consider STEM careers by countering gender stereotypes through relatable role models, promoting STEM confidence through STEM workshops and hands-on activities, and encouraging alignment between cultural and STEM identities through community-based STEM projects that develop leadership skills. Since 2015, the program has impacted 453 students who in turn have reached more than 42,777 people in Puerto Rico through their STEM Ambassadors projects. A robust mix-method evaluation of the 2020 and 2021 cohorts demonstrates significant improvements in participants’ STEM attitudes and science identity, as well as in their self-perception as a leader, confidence in their ability to succeed in science, knowledge about STEM careers and opportunities, and access to STEM role models. Moreover, 95% of participants intend to continue participating in STEM activities after the program and overall scores for the entire survey were significantly higher after the program than before. We discuss lessons learned for other programs seeking to empower girls from historically underserved backgrounds in STEM.