No teacher on continuing tenure shall discontinue his services with any controlling board except by mutual consent, without giving a written notice to said controlling board at least 60 days before September first of the ensuing school year. Any teacher discontinuing his services in any other manner than as provided in this section shall forfeit his rights to continuing tenure previously acquired under this act.

    (1) Any controlling board upon written request of a teacher may grant leave of absence for a period not to exceed 1 year, subject to renewal at the will of the board. Additionally, a controlling board may grant a leave of absence because of physical or mental disability without receiving a written request from a teacher for a period not to exceed 1 year, subject to renewal at the will of the controlling board. A teacher who is placed on an unrequested leave of absence has the right to a hearing on the unrequested leave of absence in accordance with the provisions for a hearing in section 4 of article IV. A leave of absence does not serve to terminate continuing tenure previously acquired under this act.

    (2) As a condition to reinstating the teacher at the expiration of the leave of absence, a controlling board may require a teacher who is on an unrequested leave of absence due to physical or mental disability to furnish verification acceptable to the controlling board of the teacher's ability to perform his or her essential job functions.