Mo. Rev. Stat. § 294.024
A child who has passed the child's fourteenth birthday but is under sixteen years of age may be employed in any occupation other than the occupations prohibited by this chapter, except that the child may not be employed during the regular school term unless the child has been issued a work certificate, a work permit issued pursuant to the provisions of this chapter or an exemption issued by the director.
(L. 1957 p. 525 § 3, A.L. 1989 H.B. 461, A.L. 1995 H.B. 300 & 95 merged with H.B. 414)