That depends. Usually child support ends at 18 (or when the child dies, marries, or becomes otherwise emancipated), but certain states like MO also have provisions for continued support into early college. Check the terms of your Judgment to see what the obligation is exactly, and seek the advice of an attorney in your area if it's unclear. Good luck to you!
Contact your local office of the Missouri Family Support Division at 1-800-859-7999. I agree with the prior answer that tells you to look at your court order for support. It should clearly define a termination of support provision.