High schools are spaces where adolescents learn, and their learning is not restricted to the official curriculum. During and after the school day, young people learn lessons about themselves, their peers, and the broader social world. These lessons matter not only for how they shape who young people become, but also for youths' experiences of schooling in the present. Much of the literature about high schools concerns the former, analyzing how features of adolescents' schooling predict metrics like academic achievement and attainment, labor market outcomes, and interactions with the criminal justice system. However, these studies largely overlook the latter, which I center in this dissertation. I examine youths' school-based non- curricular learning experiences across two contexts: on extracurricular debate teams and in forbidden in-school snack markets.Drawing on multi-sited ethnographic fieldwork conducted from 2017-2018 and 2019- 2022, I show that learning outside of the formal curriculum influences students' perceptions of themselves, of the formal curriculum, and of schooling more generally. Through debate team participation, students develop a strengthened sense of the importance of their own voice. They also use the skills and information that they learn in debate to improve their learning practices and make connections between the formal curriculum and other domains of their knowledge. In this way, students' extracurricular learning can strengthen their engagement with the formal curriculum. On the other hand, through illicit snack markets, students learn that adults' punitive orientations relate more to their imagined, future failures than actual risk. While youth saw snack sales as harmless and appreciated their capacity to provide appealing food options (for buyers) and much-needed income (for sellers), adults linked snack markets to drug markets, producing a stigma around the activity and punishing kids for behavior that could, instead, be viewed as entrepreneurial. In scenarios such as these, students' learning outside of the formal curriculum can lead youth to disengage from the formal curriculum and resist the demands of schooling. Overall, this work considers the ways in which students' experiences of schooling relate to the official and hidden curriculum of the high school.