If moneys in the state general fund are insufficient to make all payments to school districts, the superintendent of public instruction shall prorate the payments on a fractional basis. As additional moneys come into the fund, payments may be made until the school districts receive all moneys to which they are entitled. If an appropriation made by the legislative assembly is inadequate to meet all claims against the appropriation and is therefore the cause of the insufficiency, the prorated fractional payments made under this section constitute payment in full.