We had to deal with this 10+ years ago.....
SCENE: Under 1 minute to go, leading team (21-7) when they recovered a fumble at A's 5.
ACT I : QB yells "I'm taking a knee" and does. Big ole' Bubba (LB) decks snapper

ACT II : Fight breaks out , 3 players DQed

ACT III : Both coaches agree to end the game.

EPILOGUE : Safety is the top priority in high school sports. It became my job to 'invent' a cure. I felt I didn't need to re-invent the wheel if somebody/some state had already had. I found such in the Ohio Gold Book. We adopted theirs which went sorta' like this ...
A. If the team is leading by less than nine, play as always.
B. If player or coach announces to ref, "We are taking a knee"; ref then announces <"TAKING A KNEE, LAY OFF..LAY OFF."
c. QB needs to take snap and knee, any delay would kill the play. If QB than ran with the ball, play killed & QB gets USC.

D. Any B player contact is PF & DQ if flagrant.
Introduced this at next years Coach Clinic and had full acceptance as they also agreed that safety and sportsmanship are vital to high school football.