Was at a tournament last year where the opposing team clapped in unison loudly as the opposing player tried to serve. Ref stopped the conduct after a few times. Figured that was offensive enough warrant intervention.
Have had several refs stop students from stomping during serves.
Last year, it was always fun to watch Sullivan South's pep squad show up with the brooms waiting on the sweep. Didn't particularly like them cheering against our kids, but they were for the most part, a well behaved, loud group of fans.
Ken