Unfortunately, the hands of teachers are tied. They can't sit a kid in the corner or separate a group of mischief-makers without parents raising holey hell, complaining to the board, and getting lawyers involved.
One of the great undiscussed tragedies in America is how our school system has basically been castrated when it comes to treatment/discipline of kids and separating the good from the bad.
My mom told me how she had a little turd who basically refuses to participate and just wants to color on herself...can't do anything and if she tries, the parents raise a stink, call lawyers and administrators, etc. When that one wants to totally check out and take a nap. Do you know what they have to do? One would think, send her home, nope parents don't want the little heathen. Teachers have to let this little princess go take a nap. Here's the kicker. One of the few rooms there is to spare just for princess nap time sometimes is occupied by a really great advanced kid doing extra work.
Now, I ask you, guess who wins that battle? The pain in the ass who is going to be a drag on society or the advanced student who is going to be an asset like a doctor, engineer, etc...?
That's one story, of thousands over the years I've heard from my mom. I've known shit was going to go south for a couple of decades, because I've heard first hand from a teacher on the frontlines what is coming down the pipes via the educational system...bad and or worthless kids via bad and/or worthless parents and the cycle perpetuates itself because nobody can attempt to correct it via real education and some discipline.