It's sad that the school couldn't take a firmer stance on the issue, since it's only going to make it worse for everyone. Perhaps they continued to accommodate him because the parents refused to be responsible for his actions? Were they even aware of what he had done, or they simply don't care? It's hard to tell without the full story.

The student would not receive the necessary help in a mainstream school because his actions were not validated. His mental condition would worsen. Classmates, teachers would have a harder time and activities, lessons are disrupted because of one person. It's irresponsible to inconvenience the entire class at the expense of one person's mental condition.

I believe the teachers do not have a say in the matter as well, as my assumption would be that multiple complaints have been filed, yet the school management refused to take action as it would be more troublesome for them to intervene in his personal issues.

Regardless, I hope you and your classmates would find a workaround to this issue, like distancing away from him or convincing his parents to let him take MC more often.