Mo. Rev. Stat. § 171.027

Any provision of state law that requires a school district to conduct an election of the voters of the school district in order to adopt a four-day school week shall not apply to any school district that had a four-day school week in the 2023-24 school year and that contains all of a city with more than two thousand one hundred fifty but fewer than two thousand four hundred inhabitants and is located in a county with more than nineteen thousand but fewer than twenty-two thousand inhabitants and with a county seat with more than two thousand two hundred twenty but fewer than two thousand five hundred inhabitants.