You have to have a life. Or you'll be resentful and they won't respect you, because they'll resent that you resent them. So get a life, insist on having time for just YOU and let them know when that time is going to be.

You also have to be there for them, which mostly means open to actually listening to them. They may be insane by adult standards, but their own logic makes sense to them and is very real, and imposing your own logic isn't going to work. If you want the respect of a teenager, it's useful to respect them first. If you never see them, then begin insisting on time just for THEM individually as well as time just for YOU.

Yes, boundaries are needed, and you're going to have to hold tight as they test the boundaries, but so is understanding and space. The kid has to know that no matter how ashamed you might be about any mistakes they make, you still actually *love* them, and are willing to let them make some mistakes so that they can grow from it, and are willing to help them to learn how to pick up from their mistakes.

So, why is the kid not going to school? What's the problem? Why does the kid think that the only solution to the problem is to not go to school? Is it the wrong school? Is the kid being bullied and has no way to solve it? Is the kid not interested in normal measures of success and needs to do something *real* for a change instead of more paperwork and homework and boring stuff that the kid'll never use in the real world? Does the kid not have any clue about what the kid wants to do in the future and therefore has no REASON to go to school?

There are so many things this could be, and the only way you're going to know which boundaries are important in this situation is by listening.