Design2Learn (D2L) is an afterschool program aimed at increasing science interest, engagement, and achievement among middle school students who historically have been underrepresented in STEM. The D2L model, designed and implemented by ExpandED Schools, uses three core strategies to foster students' interest and engagement in science: (1) collaborative teaching between an in-school science teacher and two afterschool educators; (2) curricular bridging, which connects in-school science instruction with afterschool activities; and (3) design-based learning, which emphasizes hands-on activities and inquiry-based instruction. To support implementation of the program, ExpandED Schools and its partner, the New York Hall of Science (NYSCI), provided participating educators with a week-long professional development (PD) institute in the summer, occasional Saturday workshops, strategic planning sessions, and regular on-site coaching throughout the school year. D2L was designed as a three-year intervention, serving students in 6th through 8th grade. In 2016, the U.S. Department of Education Investing in Innovation (I3) program awarded ExpandED Schools a development grant to support the design and study of D2L. The Research Alliance for New York City Schools served as the external evaluator of the program and conducted a randomized control trial to assess the impact of D2L on key student outcomes. As part of this study, researchers randomly assigned 32 afterschool programs to offer D2L or be part of a control group that offered their usual science programming. Using mixed methods, the study examined D2L's implementation, as well as its impact on students' interest and engagement in science, their attendance, and their science grades. Findings suggest that there may not have been a substantial difference between the D2L and control experiences, and students may not have received adequate exposure to the intervention to influence students' interest and engagement in science or science achievement.