Whoever wrote you divorce agreement was confused about what they were doing.  You cannot limit your right to child support by an agreement--so the divorce decree is not controlling, california law is.  Many parents enter into agreements attempting to limit child support.  Courts encourage settlement agreements—even those regarding child support.  However, “such agreements, to the extent that they purport to restrict the court’s jurisdiction over child support, are void as against public policy.  In re Marriage of Bereznak & Heminger, (2003) 110 Cal. App. 4th 1062, 1069. He has to pay YOU support until one of the following happens:  1)she turns 19 or 2) she graduates from High school.  See the following family code section:Family Code Section 3901: The Duty to Support Minor ChildrenThis section provides the following:(a)The duty of support imposed by Section 3900 continues as to an unmarried child who has attained the age of 18 years, is a full time high school student, and who is not self-supporting, until the time the child completes the 12th grade or attains the age of 19 years, whichever occurs first. (b) Nothing in this section limits a parent’s ability to agree to provide additional support or the court’s power to inquire whether an agreement to provide additional support has been made.So, you can tell your ex that he has to keep paying.  If he doesn't--I would recommend seeking help from a local family law attorney in enforcing the judgment.Best of luck.