As of March 2015, the American Youth Soccer Organization allows players between 4 and 19 years old. AYSO divisions are split by age group. Teams are typically organized by gender, though many U5 programs include boys and girls on the same team.
Divisions range from U-5 to U-19. The "U" stands for "under" since the player should be under the specified age prior to the beginning of the season. If a particular region has a "play up" policy, players can usually move up to a higher age division if they desire. For example, a 6-year old can play on a U-8 team with 7 and 8 year old team mates. Older players, however, cannot join a team in a younger age division.