Michigan Compiled Laws, Chapter 38. Civil Service and Retirement § 38.92

Sec. 2. If a teacher on continuing tenure is employed by another controlling board, the teacher is not subject to another probationary period of more than 2 years beginning with the date of employment, and may at the option of the controlling board be placed immediately on continuing tenure. A notice provided under section 3 of article 2  1 shall be given not later than 60 days before the completion of the probationary period. If a teacher on continuing tenure becomes an employee of another controlling board as a result of school district annexation, consolidation or other form of school district reorganization, the teacher shall be placed on continuing tenure within 30 days unless the controlling board, by a 2/3 vote on an individual basis, places the teacher on not more than 2 years' probation. However, if such a teacher is under contract but not on continuing tenure with the employing board as of the effective date of the amendatory act that added this sentence,  2 the teacher is not subject to another probationary period of more than 1 year beginning with the date of employment.