High school baseball is not necessarily nationally governed. That is to say state and regional High School Athletic Associations take precedence when setting rules for high school baseball play. However, the National Federation of State High School Associations seeks to bring together a consensus and suggest rules to their members to adopt. Many of the professional tenets and rules of baseball remain the same when it comes to playing high school baseball, though some rules, particularly in regard to substitution are different.
While it is not required, it is suggested that head coaches list all players on their teams when swapping line-up cards at the start of the game. This will make the announcement of substitutions faster. According to the National Federation of High School Associations, an official substitution is made when the umpire chief is notified of a substitution during a dead ball situation by the head coach. The umpire then notifies the opposing head coach and the official scorekeeper. The substitution is logged by the umpire.
Some high school leagues allow for courtesy runners for pitchers and catchers who reach base. A courtesy runner may take the place of the pitcher or catcher on the base paths without officially entering the game. The same courtesy runner may not be used for both the pitcher and the catcher, and the courtesy runner may not also enter the game in the same half inning. This prevents a courtesy runner from scoring, and then pinch hitting immediately thereafter.
Some high school baseball leagues allow players to re-enter the game after they have been substituted for during game play. Sometimes this rule is also limited to starters. This allows high school managers to pinch hit or pinch run for a starter, and then return him to the field in the next half inning. The caveat to this rule is usually that once a pitcher is removed from the pitcher's mound, he cannot return to pitch in the same game.