Varsity players are a bit more skilled (at least most are
and I expect them to play under control a bit more. I'd have to base that one on the skill level of the players. If displacement occurs then ring them up otherwise look at the history, If the teams are getting too physical then I bang em, if there is an occasional bump every once in a while I might let it go if the kid is able to maintain position for the most part. As for Varsity, and better JV teams for that matter, a B/C is a bit more obvious that a foul has taken place, the hard part is determining who earned the foul.