The really annoying thing is that fear of getting caught isn't holding them back anymore, so the adage that there is strength in numbers doesn't even hold true.
DS12 got jumped by two classmates a few days ago after school. Right after school, when he was completely surrounded by the cars of parents waiting to pick up their children. DS walks home, so we were not there, but several parents called the Principal within minutes of the incident. How stupid do you have to be to jump another kid in full view of 100 parents?
The upshot after several meetings between the Principal and all the boys involved is that all three of them have been given notice that if there is another incident involving the same people, all three of them (including DS) will be suspended, which is EXACTLY what I expected. DS doesn't understand how he can be the victim and still get punished, but I told him that that is how it almost always works when it comes to fighting at school; if you are one of the combatants you get punished, even if you are on the losing end of the situation. (Even 40 years ago when I was in school that was the rule -- we were subject to suspension if we even got caught watching a fight.) He verbally provoked them, so he is being held accountable for his actions, too.
I'm hoping that he has learned a lesson about keeping his head down and watching who he chooses to smart off to, but the bottom line is that no verbal provocation deserves getting held in a chokehold by one guy while another one gut-punches you. Of course, we are not privy to whatever additional punishments the two boys might have received. AFAWK, the school is treating this as a one-free-bite situation, but I'm hoping that they step up the general monitoring and warnings a bit more. All puns aside, the kids need to have the fear of God instilled in them, because they should be scared cross-eyed of the consequences of getting caught roughing up another kid.