Goodness, he just doesn't seem motivated at all. I'm not sure how much you can do at this point that you haven't already tried. It may be has to just face the consequences of failing. I think there comes a point when you have done all you really can. It's not like at 17 you can make him go to his room without supper .

I'd say you really have tried, and he'll have to just face the consequences of his actions..

But I don't have any children myself so perhaps someone else will have better advice for you. I know it has to be tough for you!