Mo. Rev. Stat. § 165.051
If any school district has money in the teachers', incidental, capital projects or debt service fund not needed within a reasonable period of time for the purpose for which the money was received, the school board in the district, if it deems it advisable, may invest the funds in either open time deposits or certificates of deposit secured under the provisions of sections 110.010 and 110.020; or in bonds, redeemable at maturity at par, of the state of Missouri, of the United States, or of any wholly owned corporation of the United States; or in other short term obligations of the United States, or in any instrument permitted by law for the investment of state moneys. No open time deposits shall be made or bonds purchased to mature beyond the date that the funds are needed for the purpose for which they were received by the school district. Interest accruing from the investment of the surplus funds in such deposits or bonds shall be credited to the fund from which the money was invested.
§ 165.051, RSMo