In General, FIFA Rules Apply. Modifications listed below
Recommended number of players on the field for each age division: These numbers are based on the final number of players per team (after late registrations) and AYSO short-sided games guidelines. In brackets you will find the recommended length for each quarter of play.
U-6 -- three or four per team on field (3 v 3 or 4 v 4); with no goalkeepers [5-7 min quarters with 5 minute half-time break]
U-8 GIRLS/BOYS -- four or five per team on field (4 v 4 or 5 v 5); with no goalkeepers [10 minute quarters with 5 minute half-time break]
U-10 GIRLS/BOYS -- seven to nine per team on the field (7 v 7 to 9 v 9) one of whom is a goalkeeper. [12.5 minute quarters with 5 minute half-time break]
U-13 -- eleven per team on the field (11 v 11), one of whom is a goalkeeper. [12.5-15 minute quarters with 5 minute half-time break]
Divisions U6 through Over 13 Spectators: Team coaches, player substitutions and spectators are to remain at least 5 –6 yards from outside the touch line and no closer than 5 yards from the goal line. No individual is allowed to run the length of the field except the participants of the game.
AYSO codes of conduct are to be followed (see ABCs of AYSO magazine). Coaches may give direction to players when they are “off the ball”. Spectators may cheer for any/all players.
Match Guidelines for parents, teams and volunteers:
Only AYSO registered players assigned to the team or practice site may participate in matches. Teams are to have player forms for all players on the team at all practice and match sites. A parent/guardian is expected to be present at practices and matches. Official lineup Cards are to be completed for each match. Respect of the rules and guidelines of this Region is expected by all. Team rituals are encouraged that involve parents and players. A handshake prior to the match beginning is encouraged. Coaches are instructed to sit back and take notes during the matches. Knowledge of this regions policies is the responsibility of it participants.
Field of Play. Approximate sizes as Parks have various markings and green space variations.
The Ball. Size appropriate for division.
Number of Players. Players on the field should be equal on each team, with the exception of, if a team is down by 4 goals they may play with an extra player. AYSO players present at game time shall play a minimum of 50% of each game and no player shall play 100% of the game unless every other player has played 75% of the game.
Duration of the Match. The Referee is the official time keeper for each match. Teams and team players preparedness will assist in the matches starting on time. The basic time structure for the match schedule includes a 5 minute half and 15 minutes between matches. Regardless of the issues that arise, the first matches are to end 5 minutes prior to the start of the next game.
Substitutions are ALLOWED THREE TIMES DURING THE MATCH; half way through the first half, at half-time and half way through the second half. This season there will be another optional substitution point half-way through the 4th quarter (to allow even playing time) An injured player who is unable to continue may be substituted with the consent of the referee.
Player Equipment: Shin guards are mandatory to participate in practices and matches, and shall be worn with socks covering them. Full uniform shall be worn at each match, with shirt tucked in. Tennis shoes or soft cleat soccer shoes are appropriate footwear. Dangerous cleats may not be worn.
Referee & Assistant Referees: The game authority figure. Responsible to inspect the playing fields and check player equipment prior to each match time. Assist to, facilitate matches begin and end at the scheduled times. Volunteers trained at AYSO clinics and supplied with a referee uniform. Referee decisions are final on points of fact connected with the match and are not to be challenged. Referee and assistant referees shall be registered with the National Office. Assistant Referees shall occupy the area near touchlines; from half line to the goal line positioned opposite of each other. FIFA laws apply: one referee, two assistant referees and a fourth official.
Referees are assigned to games by the Referee Administrator. If no referee is available the coaches should agree on who will referee. Each Coach may Ref half the game or if they agree, one Coach or competent parent may Ref the whole game.
The Start and Restart of Play: FIFA laws apply with exception of age appropriate decreased number of yards from center mark while kick of is in progress. Restarts after the breaks in the first and second halves will be taken at the same junction it was interrupted. (i.e. the ball goes out of play over the goal line; the referee stops play for substitution break, after two minutes at the most, play is restarted with a goal kick or corner kick, depending upon who is awarded the ball) Ball in and out of Play & Method of
Scoring: FIFA laws apply.
Offside: U10 and U13 divisions only. FIFA laws apply.
Fouls and Misconduct: Red and Yellow cards are not used, referees are to deal with infractions verbally and may remove a player or spectator based upon FIFA laws of conduct and/or AYSO player, parent, & coach conduct codes. Slide tackling is considered dangerous play. Heading is considered dangerous play for all divisions except U13 and U10. Coaches should allow players to refrain from heading if they wish.
Free Kicks, Corner Kicks, Penalty Kicks, & Goal Kicks: FIFA laws apply with exception of age appropriate decreased number of yards from the ball. Free kicks are indirect for all divisions except for penal fouls in U10 B/G and U13 Coed. Direct Free kicks will be taken for the penal fouls in U10 B/G and U13 Coed. Penalty kicks are awarded in U10 B/G and U13 Coed divisions only.
Throw ins: FIFA laws apply, with AYSO referees making exceptions to teach rather than to give over possession based upon technique of throw in.
Links:
Here's a nice visual explanation of offsides - takes about 5 minutes.