this topic has come so far off of the wheels. lets all agree that there is a shared responsibility for these actions on part of the players, parents and coaches.
parents place their children in the trust of the school and coaches. The coaches are obligated to provide and maintain a safe, protected and supervised environment for the welfare of these kids while in their care. otherwise schools should insist that parents attend and care for their own children while at such events.
the parents are not excused from their responsibility but count upon the coaches and school to provide as stated above in their stead while the children are in their care.
the students are immature for displaying such poor judgment.
ultimately, at the time of the infraction; the coach and staff are responsible for not preventing this from occurring.
you teach your kids not to play with matches but they burn down the house while the babysitter is on the phone instead of watching the kids as hired to do... who is at fault?