This article presents the findings of a 3-year case study that examines the lasting effects of having participated in cogenerative dialogues during a 9th grade science experience. Theo, a high school student researcher of more than three years, affords insights into the expansion of human agency, attributing it to his consistent participation in and the ripple effects of cogenerative dialogues. Three vignettes that underscore the value created by (a) coteaching with a high school science teacher, (b) being a peer tutor and (c) creating an inter-grade school wide curriculum project are examined as Theo moves through 10th and 11th grades. This study provides insights into how students who have traditionally participated in science peripherally can access structures that enable them to contribute to their own learning and the learning of others centrally and in substantive ways. Educators can learn and take away from this study feasible means by which students and teachers can work together to transform students' science identities and teachers' perceptions of what students can do with their newfound science agency.