Yes, that is because they are required to have continuing education - and you might as well get your doctorate if you are required to take classes. It is definitely not a requirement for the job. The vast majority of the time it is something obtained AFTER getting the job.
To qualify for a School Administrator Certificate in Michigan you must earn a master’s (or higher) degree at a regionally accredited college or university that has been approved by the Michigan Department of Education.
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The School Administrator Certificate must be renewed every five years to continue leading at the building level. The renewal process involves taking coursework at the college level or participating in state continuing education classes or district-provided professional development classes, as follows:
Six semester hours from an accredited college or university, either as appropriate content and grade level courses or in a planned course of study; or
There was a thread recently, about college enrollment in Michigan. Overall, the drop in enrollment is in line with the drop in population of the state, something like 9%. U of M and State are the only colleges showing an increase in enrollment, while the second tier schools are seeing enrollment declines of 20-40% over the last 10 years.
What my comment about U of M going “all out-of-state, all the time” was based on the spread between in-state and out-of-state tuition, vs WMU, a second tier college. Western charges out-of-state students 126% of what it charges in-state. U of M charges out-of-state students 330% of what it charges in-state. U of M accepts twice the percentage of in-state applicants, as out-of-state, to get close to a 50-50 balance between the two. My math says that U of M could, hypothetically, completely fill the campus with out-of-state students, and make a big pile of money, if that was the only objective.