(a) Elections for the purpose of voting special taxes for any school purpose or for school purposes generally under the constitution may be held at any time in accordance with law for one or more of the following purposes:
(1) Voting such tax where no such tax is being levied;
(2) Voting such tax for a period additional to the period for which the tax then being levied has been voted;
(3) Voting an additional rate of such tax where such tax has been voted at a rate less than the limit permitted by the constitution;
(4) Voting such tax for a different purpose from that for which the tax has already been voted and beginning with the fiscal year after such election, the purpose of the new election shall govern; provided, that the change of purpose for which a tax is voted shall not deprive the holders of outstanding warrants of their rights; or
(5) Voting such tax for the purpose of consolidation or enlargement of special tax districts; provided, that the holders of outstanding warrants shall not be deprived of their rights.
(b) No election for the voting of the tax shall be held which would authorize the tax for a period or aggregate periods which would cause the tax to become due and payable later than 30 years from the October 1 next after such election. All warrants heretofore or hereafter issued as preferred claims against a special tax under the constitution shall continue such claims against such tax until paid, whether such tax was voted at one time or from time to time and whether such tax was voted at the time the warrants were issued or thereafter.