A school district that for school purposes imposed on agricultural property a proportionate tax rate different from the school district levy on other taxable property, as permitted by repealed sections 15-53.1-37 and 15-53.1-38 on December 31, 1984, shall continue to levy the proportionate tax rate unless the school board is directed, by a majority of the district's qualified electors voting on the question, to discontinue the proportionate tax rate. No other school board may impose a proportionate tax rate on different classes of property within the district.
N.D.C.C. § 15.1-12-23