Intervention needs to occur before injuries such as this.
We used to isolate violent students in special schools where there was tight discipline and the instructors were able to cope with boisterous students. This accomplished two purposes. The removal of the violent students allow the rest of the students to learn without fear of abuse. The more structured environment gives the opportunity to create better self discipline amongst the violent students and foster a climate where they too might succeed.
The loss of the ability to segregate violent students, the loss of the ability to enforce consequences for bad behavior created by the insane liberal drive to ignore both ability and effort has caused the total breakdown of the education system. The forbidding of religion and traditional morality and the forced consumption and participation in immoral ideology imposed on students is contributory.
I've always thought that students that are incorrigible should be sent to reform schools run by United States Marines on a boot camp model. I've also felt that parents should not have a say in this. If they can't control their children, someone else should have that duty.
I've envisioned that if a school principal decides a student is incorrigible, he/she gets handcuffed, and a military van picks him/her up to take him/her to the boot camp. The parents will be notified after the fact.