From the Greater Good Science Center at the University of California, Berkley, Vicki Zakrzewski, Ph.D writes about the benefits of adolescents becoming involved in a community service project. She describes the benefits as not only positive attitudes, but physical improvements, as well:
Dr. Zakrzewski further describes optimal structures for school-based community volunteering programming. Direct contact with the population in need provides the adolescent with the best overall positive experience.
For more information, here is her entire article.