The board shall levy as many cents per $100 assessed valuation on each class of property in the county or in the area of a preexisting school district, as the case may be, as will produce the amounts, according to the last assessment, shown to be necessary by the statement in the following order:
First, for the bonded debt and for the contractual debt not bonded, if any, of any school district of the county existing before May 22, 1933, and incurred before the adoption of the Tax Limitation Amendment;
Second, for the Permanent Improvement Fund;
Third, for general current expenses.
The rates of levy for each purpose may not exceed the amounts fixed by section six-c unless another rate is authorized by the Tax Commissioner or set by the Legislature in accordance with this article. When less than the maximum levies are imposed, the levies on each class of property shall be in the same proportions as the maximums authorized.