Project Summary/Abstract: Exposing students to new opportunities, creating a sense of accomplishment, social learning through informal mentorship, and making learning fun have been found as benefits of informal STEM education. The Science & Health Partnership at Yale Center for Medical Simulation leverages advances in simulation training to promote informal STEM learning for underrepresented high school students in an urban environment. The proposed work builds on the Simulation Academy at Yale – Youth Entering Science (SAY-YES!) research team's prior innovative work developing an after-school simulation program engaging local public high school students in hands-on experiential learning using multiple technologies including high fidelity mannequin simulators to explore anatomy and physiology. This five-year SEPA proposal seeks to develop, from the foundations of the existing SAY-YES! program, a multi-level curriculum for STEM learning, leadership, and mentoring. The specific aims for this project are to: 1) develop and implement a scalable four- year curriculum for 9th-12th graders and model of instruction including focused opportunities for STEM peer- leadership education; ; 2) create a longitudinal mentoring program designed to foster mentoring communities that value STEM engagement, performance, and representation through modeling behavior and encouraging of growth mindsets in our SAY-YES! students; and 3) determine the proximal and longitudinal benefits of the program through an iterative design-based-research approach to assess outcomes of both students and educators participating in the program. Through hands-on experiential learning activities, students will activate both situational interest in specific STEM applications as well as develop lasting gains in their self-efficacy and value beliefs. This will motivate future STEM engagement and career trajectories. Since most US cities have at least one academic medical simulation center with a rich, high technology environment for hands-on informal learning, SAY-YES! will provide evidence to recommend broad dissemination as a framework for STEM engagement for underrepresented students across different urban environments.