Mo. Rev. Stat. § 304.075: School bus signs to be removed, when — misdemeanor.

1. Any motor vehicle which is not regularly being operated by a school district or under contract with a school district or by private schools for the transportation of school children shall not bear signs indicating that it is a school bus. When any person operating a school bus under contract with a school district uses it for purposes other than for the transportation of school children, the person shall cover the signs thereon in such manner that it will not appear on the highways as a school bus.

2. Any person violating this section is guilty of a class C misdemeanor.