Most state high school baseball associations issue their own game-ending regulations, so high school umpires must check their local state associations and know the rules for their state.
If a state association has made game-ending rules, they must be followed, even if the coaches of the two teams want to agree on and use some other rules.
If the game is being played in a state that does not have its own game-ending rules and the coaches want to make some agreement on what rules they want to use for that game, the umpire can agree to what they want to do. However, the coaches need to let the umpires know what they want before the game begins.
However, if a state has not adopted its own game-ending rules and coaches have not come to their own agreement on what should be done, a high school umpire would follow the NFHS rules found in rule 4:
If a game is tied at the point of stoppage, it is declared a “tied” game. There is no winner.
If a game has gone enough innings to be official (4.5) and the game has to be called, then:
If the home team is ahead, they win
If the score is tied or the visiting team is ahead, the game score reverts back to what it was at the end of the last completed inning