Sideline Warning/Interference

[tankmjg24]

I have a middle school game coming up that involves a team with a history of ignoring sideline rules. They have 4 coaches and each one of them wants to be out at the numbers signaling plays. I have heard that there has been instances of them being on the field during live play too. I will be the official on their sideline, and I am curious how you all would go about enforcing the rules. I hate to sit and warn all game or throw flags, which is why I am asking for opinions. Thanks.