If the child is emancipated child support payments cease.
They also cease if the child turns 18 and is not in school.
The best thing for your child to do is to get back in school or at least get their GED.
I would think that if you can show the courts that the child is not living with the other parent some sort of modification would be in order. The child testifing to this fact would go a long way I would guess. One thing to consider is how soon will the child turn 18.
If your paying through the NC Child support office I would give them a call and explain what is happened they may be able to tell you how to proceed