School and has no job.. do I still have to wait until he turns 21 ro come off child support?

What state and country is this in? Actually in many states of the USA he's an adult at 18. Was there a court order for support to continue to 21 issued?

What does the Child Support Order say? That's the controlling document.

The answer to me is most likely no, but it will depend on the exact wording of your child support agreement.