Mo. Rev. Stat. § 205.850

The county commission in counties of the third and fourth classes may in its discretion, with an order of the juvenile court showing approval, appoint a county superintendent of public welfare, and such assistants as it may deem necessary. Whenever the county commission of any county has appointed a superintendent of public welfare such officer shall assume all the powers and duties now conferred by law upon the probation or parole officer of such county and shall assume all the powers and duties of the attendance officer in said county and all the powers and the duties of the attendance officer in any incorporated town or village having a population of more than one thousand inhabitants, and no other or different probation or parole officer or attendance officer or officers shall be appointed by the judge of the juvenile court, by the county superintendent of public schools, or by the school board or any incorporated city, town, or village school district or consolidated school district.