Here is the Texas Code on when Child Support Ends In Texas:

Sec. 154.001. SUPPORT OF CHILD. (a) The court may order either or both parents to support a child in the manner specified by the order:

(1) until the child is 18 years of age or until graduation from high school, whichever occurs later;

(2) until the child is emancipated through marriage, through removal of the disabilities of minority by court order, or by other operation of law;

(3) until the death of the child; or

(4) if the child is disabled as defined in this chapter, for an indefinite period.

When does child support end in Texas, inforgraphic
texas child support book

Here are the Texas Child Support Laws, all provided in this free download:

Texas Child Support PDF

Please note this is the actual laws from the statutes on Child support and is not an interpretation or manuscript explaining the laws.  This is useful to have printed and ready for your hearing involving child support in Texas.