Verified answer

From the HSLDA website:

The Supreme Court of Michigan ruled that nonessential elective courses offered to public school students must be offered to resident nonpublic school students on a shared-time basis. Snyder v. Charlotte Public School District, 365 N.W.2d 151 (1984). The Michigan Department of Education has interpreted this case to mean that both nonpublic and homeschool students may enroll in nonessential elective courses at their local public school (see the department’s “Information on Nonpublic and Home Schools”). No interscholastic activities are permitted unless permission is provided by the local public school district.

I would also suggest contacting one of your local homeschooling groups for more information on sports available to homeschoolers: http://blog.denschool.com/2011/10/local-homeschool...

You need to check the homeschooling laws in Michigan. Some districts might and others might not -- call your public school and ask. There's a fair chance he will be able to play, since you pay taxes to begin with.