This book lists and describes opportunities for teenagers to participate in organized science and math activities within and without the classroom. Students may participate at the local or school level by joining clubs and interest groups and by entering fairs; at the national level, by entering competitions of various sorts; and at the international level, by competing in olympiads and other kinds of contests. The experiences of teachers and students involved in these types of activities, information about the organization and functions of activities, and survey results are described. Lists of national and international science and mathematics activities are provided. (CW)