(2) Professional educators shall be prepared, and legally certified, in their areas of assignment. Educators may not be assigned or willingly accept assignments they are not certified to fulfill. Educators may be assigned to or accept assignments outside their certification area on a temporary, short-term, emergency basis. Examples: a teacher certified in English filling in a class period for a physical education teacher who has that day become ill; a substitute teacher certified in elementary education employed as a librarian for several days until the district can locate and employ a permanent substitute teacher certified in library science.