This article investigates the development of agency in science among low-income urban youth aged 10 to 14 as they participated in a voluntary year-round program on green energy technologies conducted at a local community club in a midwestern city. Focusing on how youth engaged a summer unit on understanding and modeling the relationship between energy use and the health of the urban environment, we use ethnographic data to discuss how the youth asserted themselves as community science experts in ways that took up and broke down the contradictory roles of being a producer and a critic of science/education. Our findings suggest that youth actively appropriate project activities and tools in order to challenge the types of roles and student voice traditionally available to students in the classroom. (Contains 2 footnotes, 1 table and 8 figures.)