This paper responds to Berkowitz, Bier, and McCauley's description of effective features and practices that support character development by pushing on the question of "how" child and youth environments might "build character." Acknowledging the challenges of drawing on program evaluations and extant studies of character development to identify promising practices, the author suggests a more thorough leveraging of both theoretical work and empirical studies in other disciplines (e.g., neuroscience, cognitive science, social psychology, developmental psychology, sociology, philosophy) to theorize about potential mechanisms whereby school practices develop character in children and adolescents. Utilizing a recent developmental framework, the Foundations for Young Adult Success (Nagaoka, Farrington, Ehrlich, & Heath, 2015), the author proposes that 10 particular "developmental experiences"--specific opportunities provided for young people to act and reflect--are key mechanisms whereby settings influence the development of character and equip children and youth to build toward agency, an integrated identity, and a set of competencies that support success in young adulthood. These developmental experiences are briefly summarized and some potential alignments with Berkowitz and colleagues' PRIMED framework are noted.