Michigan Compiled Laws, Chapter 380. School Code of 1976 § 380.1146

Sec. 1146.(1)Except as otherwise provided under subsection (2) and section 475, a separate school or department shall not be kept for a person on account of race, color, or gender. This section shall not be construed to prevent the grading of schools according to the intellectual progress of the pupil to be taught in separate places as may be considered expedient.

(2) Subject to subsection (3), the board of a school district or intermediate school district or board of directors of a public school academy may establish and maintain a school, class, or program within a school in which enrollment is limited to pupils of a single gender if the school district, intermediate school district, or public school academy makes available to pupils a substantially equal coeducational school, class, or program and a substantially equal school, class, or program for pupils of the other gender.

(3) If the board of a school district or intermediate school district or board of directors of a public school academy establishes a single-gender school, class, or program described in subsection (1), the school district, intermediate school district, or public school academy shall not require participation by any of its pupils in the single-gender school, class, or program. The board or board of directors shall ensure that participation by pupils in a single-gender school, class, or program is wholly voluntary. For the purposes of this subsection, participation by a pupil in a single-gender school, class, or program is not considered to be voluntary unless the school district, intermediate school district, or public school academy also makes available to the pupil a substantially equal coeducational school, class, or program.