Mo. Rev. Stat. § 167.191
It is unlawful for any child to attend any of the public schools of this state while afflicted with any contagious or infectious disease, or while liable to transmit such disease after having been exposed to it. For the purpose of determining the diseased condition, or the liability of transmitting the disease, the teacher or board of directors may require any child to be examined by a physician, and exclude the child from school so long as there is any liability of such disease being transmitted by the pupil. If the parent or guardian refuses to have an examination made by a physician at the request of the teacher or board of directors, the teacher or board of directors may exclude the child from school. Any parent or guardian who persists in sending a child to school, after having been examined as provided by this section, and found to be afflicted with any contagious or infectious disease, or liable to transmit the disease, or refuses to have the child examined as herein provided, is guilty of a misdemeanor, and, upon conviction, shall be punished by a fine of not less than five nor more than one hundred dollars.
§ 167.191, RSMo