Women remain underrepresented in STEM fields, with a major STEM pipeline leakage occurring between high school and post-secondary education. Past research suggests that providing female high school students with opportunities for problem-solving, prosocial behaviors and working towards authentic communal goals can improve their perceptions of STEM and the attractiveness of STEM careers. Building on this prior research, we investigate Scientella, a US-based, student-run organization that provides out-of-school consulting projects, mentorships and webinars to female high school students. Drawing on the direct experiences of Scientella’s co-founders and analyzing program survey data, we explore how Scientella provides these opportunities, the benefits realized by students, and the challenges faced by the organization. Survey data show that involvement in Scientella’s activities provides students with benefits related to STEM career exploration and counter-stereotypical STEM skill development, including career discovery, industry engagement and practical experience, and the development of collaboration, communication and social research skills. The admissions of Scientella student leaders to STEM majors in selective US colleges indicates the promise of Scientella’s approach, and that providing students with opportunities to engage in STEM-themed career exploration and leadership development could be an effective strategy to increase female STEM participation in post-secondary education and the pursuit of subsequent career opportunities.