Sounds like this stuff was off the field of play after the game had by ended. That would be the school admin's and police officers problem.
Player saftey is within the Ref's control on the field but off the field the school and police should be looked at very hard for the actions they did not take in this case.
If the player was hurt (slamed to ground) during play in a tight crowd in front of a goal I can see how that could be missed. (depending on how it happened)
