Schools have been sweeping this stuff under the rug for decades. I knew several parents whose kids were brutalized in school. One couple called the police when the principal refused to. Several families I knew pulled their kids out of school because of bullying.
This mother needs to pull her son out of school.
Here in GA, public school systems can have their own police forces. I am against this, as it makes it too easy to sweep stuff under the rug. If I call the police because of an incident like that, I don’t want the police beholden to the school system.