My understanding that the laws of all states in this country preclude the possession of fire arms on school property for obvious reasons. I doubt that any charges against you son will be a felony since he has a bb gun as opposed to fire arm capable of discharging an actual bullet.I suggest that a criminal defense attorney be retained to represent your son given the current situation in that the last thing he needs at this young age a criminal record for something done foolishly. Most likely he will be placed on court probation and ordered to do community service work. If he passes probation, the criminal charge or charges should be dismissed.