Tenn. Code Ann. § 49-5-401: Employment and assignment generally

(a) All educators and other school personnel to be employed for the following school year shall be assigned to the several schools by June 15 next preceding the school year for which those persons are employed.

(b) If a sufficient number of educators and other personnel are not available for employment by May 15, the director of schools shall employ and assign to the several schools such educators and other personnel as are necessary to meet the needs and programs authorized by the board of education.