From our Rules Interpreter, Scott Lewis…. In case you haven’t seen this:
NFHS Rule Updates for 2019
Of particular note: Formation rules changed so we don’t have to worry about whether the team has 10 players or not; all we have to make sure is that there are at least 5 on the line and no more than 4 in the backfield (so if they have 10 players, but only 4 backs, they are legal now). – Tripping the runner is no longer legal (note that this has a specific definition of using your leg to trip; tackling by their legs is still legal) – 40-second play clock is now a Federation rule (which, as I understand it, is basically the same as Colorado has been doing it during the experiment). There are a couple other minor things in there as well.