Mich. Comp. Laws § 393.107
The period in which pupils shall be entitled to remain in said school shall be 12 years, or the board of control may, in cases where they deem it advisable, extend such time to 14 years. This section shall not be so construed as to prohibit the said board of control from dismissing any pupil within the such period for persistent disobedience, immoral conduct, or other sufficient cause, neither shall anything in this act operate to prohibit the transfer of any child over the age of 18 years to the Michigan employment institution for the blind upon consent granted by the board of control of the Michigan school for the blind, and whenever, in the discretion of said board, the transfer of any such child will be for its best interests or the best interests of the said Michigan school for the blind.
MCL 393.107