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If the other parent did not have permission to transfer the child (the court order will typically state this authority if the other party is allowed to unilaterally make decisions re: the child's education) then the non consenting parent would bring a motion for contempt. Contempt involves the willful and knowing violation of a court order, and can result in fines, an award of attorney fees, and even jail time. (If the other parent does have sole managing conservatorship they are allowed to make these unilateral decisions unless the court order states otherwise).
reference: Tex. Fam. Code §153.132
Additionally a modification of the current court order can be requested because many courts will see a unilateral and abrupt move as not in the child's best interests.