(a) The Legislature finds that it is not in the best interest of the students particularly in the elementary grades to have multiple teachers for any one grade level or course during the instructional term. Therefore, it is the intent of the Legislature that the filling of positions through transfers of personnel from one professional position to another after the twentieth day prior to the beginning of the instructional term should be kept to a minimum in accordance with the following:
(1) After the twentieth day prior to the beginning of the instructional term, no person employed and assigned to a professional position may transfer to another professional position in the county during that instructional term unless the person holding that position does not have valid certification;