Missouri Constitution
Article IX - Education
Section 5 Public school fund—sources—payment into state treasury—investment—limitation on use of income.

The proceeds of all certificates of indebtedness due the state school fund, and all moneys, bonds, lands, and other property belonging to or donated to any state fund for public school purposes, and the net proceeds of all sales of lands and other property and effects that may accrue to the state by escheat, shall be paid into the state treasury, and securely invested under the supervision of the state board of education, and sacredly preserved as a public school fund the annual income of which shall be faithfully appropriated for establishing and maintaining free public schools, and for no other uses or purposes whatsoever.

Source: Const. of 1875, Art. IX, Sec. 6.