Mo. Rev. Stat. § 321.160

Whenever a district has been declared duly and finally organized, the members of the board shall thereafter qualify within fifteen days by filing with the circuit clerk their oaths of office, which shall be in the form prescribed by the constitution, and such board members shall also file with the circuit clerk corporate surety bonds to be furnished at the expense of the district in an amount not to exceed one thousand dollars each, the form and amount thereof to be fixed and approved by the circuit court having jurisdiction, and said bonds to be conditioned for the faithful performance of their duties as directors.