Ok, I was wrong. I didn't realized it only pertained to CPL holders.
Here's a pretty good article from mlive
So, it's legal to carry a loaded gun into a Michigan school? | MLive.com
In Michigan, a CPL isn't required to OC in public schools, just be able legally posses firearms. I'm honestly torn on the issue. It usually goes like this: Parent OC into school, the administration freaks out, lock-down, parent explains the law, the cops are always called, the cops explains the...