I may be reading into this too much but I have sympathy for someone in her position. From the story, she appears to be poor and not in a position to defend her son from getting bullied so she did what she could—give him a weapon to defend himself—and now is in trouble for it. This is the type of case where mercy should come into play and some authority figure should expand the investigation to see if the kid was getting bullied and, if so, stop it before someone does get hurt.
I have real sympathy for her. Probably no husband, probably is hanging on in a job and trying to get by. It is not easy. The school probably does nothing and the school might be as bad as most state prisons. She is probably desparate.
I hope she and her son get some help. Maybe a local karate school could help train the son for free or something. Very sad.