One result of the growing concerns over the numbers of young people moving into science, technology, engineering and mathematics (STEM)-related careers has been the expansion of formal and informal STEM education programming for pre-college youth, from elementary school through high school. While the number of programs has grown rapidly, there is little research on their long-term impacts on participant education and career trajectories. This paper presents interim findings from a multi-year longitudinal study of three national after-school robotics programs that engage students in designing, building, and competing complex robots with the goal of inspiring long-term interest in STEM. Focusing on the subset of study participants who had enrolled in at least one year of college (approximately 480 students in 2017), this paper examines program impacts on student attitudes towards STEM and STEM careers; participation in STEM-related college courses; intention to major in STEM-related fields; and involvement in STEM-related internships and other activities. Findings include positive, statistically significant impact on multiple measures of STEM engagement in college for program participants.