I think the whole thing is too unclear to make an informed opionion. It does depend on if it was a school event.
It does remind me of my youth. We had a kid in High School get suspended for wearing a tee shirt saying "Harley's the Best, The Hell with the Rest!" About 30 of us wore the same shirt the next day and had a good old fashioned sitout in the park.
Nothing happened and the kid stayed suspended. But, the principal told us that if we set one foot on school property, we would have been suspended. That was in the mid 70s and times have changed. Or, the principal was a moron...not sure which