17yo who ignores discipline attempts

I’ve got two kids who I’m really struggling to discipline (15F and 17M). For the 17yo, I can’t do anything with him because he ignores anything me or my wife says. For example, he might go partying with his friends on a school night after being told no, then miss his early classes the next morning. Wife will ground him. He’ll go “yeah, right” and walk out whenever he wants.I can’t do anything with him. He won’t listen to grounding, if my wife or I try to take his phone he’ll just hold it out of reach (he’s 6’4) or when it’s taken off his desk he’ll find it and take it back. He’s a young adult but he’s still a kid who does dumb things and I don’t get how to do it with him. If he fights with his little brother (14M), I just don’t get what to do. Yell at him?Any advice is appreciated. via /r/Parenting https://ift.tt/2GmPn6a