Broadening participation in STEM disciplines is a major societal concern. However, researchers frequently ignore settings with high concentrations of students underrepresented in STEM due to the increased likelihood of research interruptions. This chapter describes research on CAFÉCS, which is designed to broaden participation in computer science in the Chicago Public Schools, which has a high concentration of students underrepresented in STEM. Our initial attempt resulted in a research sample unrepresentative of the program participants. After adopting a proactive ethical approach by offering incentives and developing relationships with practitioners, subsequent research samples more closely represented the population of program participants.