I'm a big fan of psychological warfare where possible to get subtle and devious revenge.
The school should be doing more about such behaviour and making sure no pupil is getting away with being unpleasant to other ones.
Our lot got revenge eventually when we were allowed to play hockey against the boys. They were savaged. Some boys thought they were too butch for shin pads. They regretted that very quickly.
I'd be on at the school to get off their arse.