Mo. Rev. Stat. § 160.021
Classes of school districts.
160.021. Classes of school districts. — The public school districts existing under the laws of this state are divided into the following classes; namely, seven-director, urban, and metropolitan school districts.
(L. 1963 p. 200 § 1-2, A.L. 1973 H.B. 158, A.L. 1997 H.B. 641 & 593) (Source: RSMo 1959 § 165.010)