[just another ref]

The officials shall penalize unsporting conduct by any player, coach, substitute, team attendant, or follower.

NOTE: The home management or game committee is responsible for spectator behavior, insofar as it can be reasonably be expected to control the spectators.
The officials may call fouls on either team if its supporters act in such a way as to interfere with the proper conduct of the game. Discretion must be used in calling such fouls, however, lest a team be unjustly penalized. When team supporters become unruly or interfere with the orderly progress of the game, the officials shall stop the game until host management resolves the situation and the game can proceed in an orderly manner. In the absence of a designated school representative, the home coach shall serve as the host management.

The younger the players, the more I would take the red line to heart. Just have 'em thrown out. If game management refuses to back you up, then do what you have to do.