Tex. Nat. Res. Code § 51.077

To secure the payment of principal and interest due on a sale of public school land and university land the state has an express lien for the use and benefit of the fund to which the land belongs. The lien is in addition to any right and remedy that the state has for enforcement of the payment of principal and interest due and unpaid, up to and including the period required to reinstate the land award and obligation.