Mo. Rev. Stat. § 245.325: Simple majority to decide election.

Should a majority of the votes of those voting upon the proposition be in favor of the change, the proposed change shall be deemed carried and the same shall be made, and the new district named and formed, and directors therefor appointed as provided in sections 245.300 and 245.335. The notice required by law to be given by said section 245.300 when the laying out of a new district is sought to be had shall be made and given, with such changes therein, as the circumstances shall require.