This paper addresses the exclusion of adolescents from public spaces through design practices and public policies. Design practices in four public settings -- commercial areas, parks, neighborhoods, and schools -- and the impact of those practices on adolescents' activities and development are explored. In addition, public policies, such as curfew laws and skateboarding ordinances, and their restrictions on teens' use of public space are examined. Lastly, recommendations on how design practices and policies can support adolescents' use of public spaces are presented.