The experiment reported here tested impacts of New Hope, an employment-based poverty intervention for adults on developmental patterns of children's participation in structured out-of-school activities, using a cross-sequential design spanning ages 6 through 19. New Hope increased participation in activities (lessons, sports, religious, clubs, community centers, service). Its effects did not vary significantly across age, time of measurement, or gender, lasting well beyond parents' eligibility for program benefits. Overall participation peaked in early adolescence, declining thereafter. Policies that enhance participation during middle childhood may have long-term benefits because structured activities can provide opportunities for skill development and adult supervision that may be especially useful for children from low-income families.