Tex. Education Code § 45.034

The board, city council or commission, or commissioners court may pledge all or any part of any of its revenues from the facilities to the payment of any bonds issued under this subchapter, including the payment of principal, interest, and any other amounts required or permitted in connection with the bonds. If revenues from the facilities are pledged to the payment of bonds, the rentals, rates and charges for the occupancy or use of the facilities must be fixed and collected in amounts at least sufficient to provide for all payments of principal, interest, and any other amounts required in connection with the bonds, and, to the extent required by the resolution or order authorizing the issuance of the bonds, to provide for the payment of operation, maintenance, and other expenses.