Mississippi Code Title 37. Education § 37-29-111

(a) When any such bonds by their terms become due and payable and there are not sufficient sums in the fund established for their payment to pay such bonds and the interest thereon;

(b) When any such bonds are by their terms callable for payment and redemption in advance of their date of maturity and shall have been duly called for payment and redemption;

(c) When any such bonds are voluntarily surrendered by the holder or holders thereof in exchange for refunding bonds; and

(d) When, in connection with the issuance of any additional bonds under the provisions of Section 37-29-109 for the purpose of financing any additional construction authorized under the provisions of Section 37-29-107, any such board shall determine to combine such new issue of bonds with any issue or issues of bonds of the same board then outstanding, for the purpose of unifying such indebtedness and utilizing the income and revenues derived from all projects or facilities operated by such board to the payment of such indebtedness, and such board shall determine that such outstanding bonds are by their terms then callable for redemption or are obtainable by and through the voluntary surrender thereof by the holder or holders thereof.