Any appointed superintendent, principal or licensed employee in any public school who is under contract to teach or perform other duties and who desires to be released from such contract shall make application in writing to the school board of the school district for release therefrom, in which application the reasons for such release shall be clearly stated. If the board acts favorably upon such application for release, such superintendent, principal or licensed employee shall be released from his contract, and said contract shall be null and void on the date specified in the school board's order.