Mo. Rev. Stat. § 168.128

The board of education of each school district shall maintain records showing periods of service, dates of appointment, and other necessary information for the enforcement of sections 168.102 to 168.130. In addition, the board of education of each school district shall cause a comprehensive, performance-based evaluation for each teacher employed by the district. Such evaluations shall be ongoing and of sufficient specificity and frequency to provide for demonstrated standards of competency and academic ability. All evaluations shall be maintained in the teacher's personnel file at the office of the board of education. A copy of each evaluation shall be provided to the teacher and appropriate administrator. The state department of elementary and secondary education shall provide suggested procedures for such an evaluation.