What do you do with a child who refuses to go to school and yells constantly?

I have a 17 yr old brother who refuses to go to school. He goes to charter school where he sets his own hours. And, he usually goes twice a week for one to two hours. He screams and yells. And he does marajuana excessively. My mother will not do anything but threaten his that she take away his phone, etc if he does not go to school or screams at him to force him to go to school. I told her to put him in a rehab or call the police or something. But, she will not listen. She says she going to do it and talks to the crisis line, police but, never follows through on what the police or crisis line tells her to do. A couple weeks ago, he started screaming and banging on windows that my husband and I who live in the house had to leave and spend a night at a motel. My thing is if he does not want to go to school then he should not have to. He can learn the hard way and get his GED at a night school or get no high school diploma at all. What do you do with a 17 year old who refuses to go to school and yells constantly. Do you force him or do you just let him learn the hard way?