I feel for you, i really do.

I think this "J" has already been given enough chances.
Ethan has a valid point and so do you. Everyone has the right to be heard and the principal is not listening !

You have obviously discussed this with them on several occasions to no avail.
Possibly time for the next step.
Some schools / teachers seem to have a "you need to learn to be more resilient" attitude. This is more than a case of being more resilient - this is bullying !
Whether you go to the education department or change schools - i wish you all the best.
No child should have to go through this and as a parent you shouldnt have to see your child go through this - it is heartbreaking !
Take care xx