"Nothing ever seems to happen"
I offer you 7 things effing schools could effing try but don't effing seem to.
Masking tape across the child's mouth. Duct tape for persistent swearing(more than 20 times in an hour, nominated child in class to keep count)
Having a large metal box in the corner of the room to put disruptive children in.Especially effective in hot weather, do not allow water, they probably don't have a nice leak proof water bottle anyway.
Water boarding disruptive children. PE benches are suitable.
Calling up their parents from the classroom and having a screaming match with them over the phone in front of the class.
Public shaving of the child's head in stripes, possibly during a whole school assembly.
Pinning out the disruptive child on the playground and putting wasps in its mouth.
Putting the child in stocks and pelting them with rotting fruit, this could go down well at the school fair.
You are right OP, the schools know nothing and do nothing. What these disruptive children need is immediate, draconian punishment, they were born bad, it would frankly have have been a waste of time and no help at all to give them consistent patient parenting and security from age 0 , they are evil, cannot be redeemed and will probably be in prison by the time your lad is heading off for university for three years of early nights.