La. Stat. tit. 39 § 812
The amount, millage rate, duration, and purpose of any tax authorized under this Part shall be in accord with the proposition voted on and approved by the electors in the special election which authorized the levy and collection of the special tax, provided that the gross millage rate of all taxes authorized under this Part shall not exceed seventy mills in the aggregate at any one time in addition to the annual five mill ad valorem maintenance tax authorized by Article VIII, Section 13(C) (First) of the Constitution of Louisiana, and the annual thirteen mill ad valorem maintenance tax authorized for the Orleans Parish School Board by Article VIII, Section 13(C) (Second) of the Constitution of Louisiana, and the duration of any such tax shall not exceed ten years; provided however, any such tax levied solely for the specific purpose of maintenance of capital facilities or installation of climate control mechanisms in existing classroom facilities may be levied for up to twenty years. All taxes previously voted that fall within the limitation imposed by this Section and which were otherwise legally voted are hereby ratified.
La. R.S. § 39:812