(a) Any county board of education and any city board of education may issue and sell interest-bearing tax anticipation warrants for the purpose of paying the costs of erecting, acquiring, providing, constructing, purchasing, altering, enlarging, improving, repairing and equipping school buildings, school playgrounds and buildings for housing and repairing school buses, and for the purpose of purchasing school buses, or for any one or more of such purposes.
(b) Warrants issued under the provisions of this article shall not be general obligations of the board of education issuing such warrants but shall be payable, as to both principal and interest, solely out of one of the following:
(1) The proceeds of any ad valorem tax voted under the constitution for the purpose of paying such warrants, or for school purposes generally, and paid, apportioned or allocated to or for the benefit of the board of education issuing such warrants;
(2) The proceeds of any ad valorem tax that may be paid, apportioned or allocated to or for the benefit of the board of education issuing such warrants; or
(3) The proceeds of any privilege, license or excise tax or taxes that may be paid, apportioned or allocated to or for the benefit of the board of education issuing such warrants.
(c) Any board of education issuing any warrants hereunder shall specify, in the proceedings authorizing such warrants, the tax proceeds out of which such warrants are to be payable and shall secure payment of the principal thereof and the interest thereon by a pledge of so much as may be necessary therefor of such tax proceeds. If any such board of education makes more than one such pledge with respect to the proceeds from the same tax, then such pledges shall take precedence in the order in which they are made unless the proceedings making the pledge prior in time shall specifically provide that such pledge shall be on a parity with or subordinate to a subsequent pledge of the same tax proceeds.
(d) Warrants issued pursuant to the provisions of this article shall constitute preferred claims against the tax proceeds out of which they are payable, subject to prior pledges, and shall have preference over claims for salaries or other operating expenses or any other purpose.
(e) No board of education may issue under the provisions of this article warrants payable out of the proceeds of any ad valorem tax if the principal and interest maturing on such warrants in any fiscal year, when added to the principal and interest maturing in the same fiscal year on all warrants of such board of education then outstanding and constituting preferred claims against said ad valorem tax, would exceed 80 percent of the annual proceeds of said ad valorem tax, computed upon the basis of the last assessed valuation on which taxes were due and payable, of the county or the district, as the case may be, as certified by the county tax assessor; provided, that if an irrevocable trust fund consisting of cash or direct general obligations of the United States of America, or both, shall be established for retirement of all or part of the principal of or interest on any outstanding warrants of a board of education, then, to such extent as the retirement thereof shall be provided for by the said trust fund (including the cash therein and all sums due to be paid by the said United States under the terms of any of its direct general obligations forming a part of the said trust fund), the said principal and interest shall be excluded from any computation for the purposes of this subsection of the amount of principal and interest maturing with respect to outstanding warrants.