34 CFR § 300.30 - Parent.
(a) Parent means -
(1) A biological or adoptive parent of a child;
(4) An individual acting in the place of a biological or adoptive parent (including a grandparent, stepparent, or other relative) with whom the child lives, or an individual who is legally responsible for the child's welfare; or
(b) (1) Except as provided in paragraph (b)(2) of this section, the biological or adoptive parent, when attempting to act as the parent under this part and when more than one party is qualified under paragraph (a) of this section to act as a parent, must be presumed to be the parent for purposes of this section unless the biological or adoptive parent does not have legal authority to make educational decisions for the child.
(2) If a judicial decree or order identifies a specific person or persons under paragraphs (a)(1) through (4) of this section to act as the “parent” of a child or to make educational decisions on behalf of a child, then such person or persons shall be determined to be the “parent” for purposes of this section.