Tex. Education Code § 26.002

In this chapter, "parent" includes a person standing in parental relation. The term does not include a person as to whom the parent-child relationship has been terminated or a person not entitled to possession of or access to a child under a court order. Except as provided by federal law, all rights of a parent under Title 2 of this code and all educational rights under Sections 151.001(a)(10) and (11), Family Code, shall be exercised by a student who is 18 years of age or older or whose disabilities of minority have been removed for general purposes under Chapter 31, Family Code, unless the student has been determined to be incompetent or the student's rights have been otherwise restricted by a court order.