Mo. Rev. Stat. § 235.140: Election of new board members, when.

1. At the general election in the year after the first full calendar year after the organization of any district and at the general election thereafter, there shall be elected by the voters of the district one member of the board to serve for a term of six years. Nominations may be filed with the secretary of the board.

2. The candidates for board member shall be elected on a separate nonpartisan ballot. The candidate receiving the most votes shall be elected. Any new member of the board shall qualify in the same manner as members of the first board qualify.