1) They're right on the facts of the play: unless the violators on the sideline actually physically encroach on and interfere with action on the field, the penalty is supposed to be assessed on the ensuing kickoff.
2) No high school athletic association is ever going to replay anything based on on-field calls during a game -- unless, I suppose, it were conclusively proven the refs were actually fixing the game. This is an awful forkup, but can't be proven to be anything worse.
3) While it can't be PROVEN to be anything worse, in my experience, while teams technically violate the sideline rules at a pretty much even rate (a very high rate, incidentally) regardless of ethic makeup, the times I have actually seen it called, probably 75% of the time is is by white refs on predominantly black teams. Something about being mouthy and uppity would be my guess.
4) OTOH of THAT, the vast vast majority of the time sideline violations are called, the violators are guilty. It's one of those rules almost everybody technically violates all the time. It's also one of the dumber rules on the books, because to enforce it, officials need to take their eyes off of what players are actually doing on the field and look at what other people are doing OFF the field.