We investigate whether the intervention designed by Kuhn and Udell (2003) to develop argument skills could be implemented productively among adolescent males in a residential juvenile detention facility--boys who were educationally disengaged and severely disadvantaged academically as well as socially. Compared to a control group from the same institution who did not participate, participants in the intervention exhibited superior argument skills following the intervention. In dialogic argumentation with a peer, they made more counterarguments against the opponent's claims, and they more often voiced rebuttals of the opponent's counterarguments of their own claims. Also, in individual arguments in support of their own positions, they offered more and higher-quality reasons, relative to the control group. In addition to these cognitive skill gains, possible enhancements in cognitive engagement and mental self-management and self-control are discussed. (Contains 1 table.)