RULES FOR HICH SCHOOL SOCCER: With next High School Soccer season coming up, it is well remember that Victor Matheson say: " One of the most annoying aspects of soccer in the United States is that every league wishes to play by its own special rules. There are separate rule books for FIFA, the U.S. Youth Soccer Association (USYSA), the largest organizer of youth club soccer in the U.S., The National Federation of High School Athletics (NFHSA), and the National Collegiate Athletic Association (NCAA). While the fundamental game is the same in all of the leagues, several important details are different in each of these leagues. These differences can cause confusion among referees, players, coaches, and parents".
DURATION OF THE GAMES: Under High School rules the half-time length is 10 minutes, and the clock is stopped after goals; when the card is showed, while the penalty kick is taking and another times that referee think that is neccesary.
CARDS: HS permit that player be replaced. Also, when player is sent-off by taunting, can be replaced.
RESTART THE GAME: after the games was stopped by injury, It must be restarted with drop ball if no team was in clear possession when play was stopped or Indirect Free-Kick if one team was in clear possession when play was stopped.
SUBSTITUTION: HS rules permit both team sustitution in corner kick and throw-in if team in possesion do it.
You can see a good article about it in: http://asktheref.com/html/article072500.htm