It is illegal for a student to have a firearm on a school campus in Michigan.
A parent or guardian may have a weapon in possession in the car while picking up or dropping off a student...but must remain in the car.
Got questions-check link:
http://www.migunowners.org/forum/index.php?
Your best solution is to park off campus and walk...leave your gun locked up in the car and get a little exercise;o)