I am so sorry for what you are going through! Yes definitely hit a meeting. When I went to Celebrate Recovery, we had many parents there and it got them through some very dark times.
You are right about his age. If he is 17 now, by the time this would even go to court he would likely be 18 or very close. My bet will be that it will go on for a while until Mom has had enough, then things may change. And of course, a change in environment can be a good one.
I have one kid in private and one went to public. There are issues with schools of all sorts. Here, the biggest private high school is a huge drug/sex den. There are some very spoiled and out of control kids, and some parents who are deep in denial, and other parents who participate themselves. It's disgusting.
Here you go to the school district where you live unless it's private. You are not even permitted to offer the pay the tuition to the public school, it's just not allowed and should not be.
Stand firm, that is the best thing you and his Dad can do at this point. Along with prayer and go to meetings! It's also not a bad idea to call the social worker/counselor at the school and explain the situation. They cannot give you any info, but you can sure give them some info to watch out for and to keep an extra eye on things.