Mo. Rev. Stat. § 50.040

Whenever there are outstanding any legal county revenue warrants of any county bearing six percent interest which will be redeemed by the taxes of the current year, and there are school moneys in the hands of the county treasurer belonging to the various districts which will not be required for the support of the public schools before the date when such revenue warrants will be paid, the county commissions are authorized to direct the county treasurer to invest such surplus school moneys in the revenue warrants, and hold them for the use and benefit of the school districts until the money for the redemption of such warrants is received into the county revenue fund, when such moneys shall be applied to their payment.