The OHSAA will police it. ANYONE can report a violation, and at that point OHSAA is obligated to review situation. We had a girls team in our area win district, and a parent on the winning team wasn't happy with coach, and reported an "illegal" player - practiced with her travel team, and they ended up forfeiting District championship, and not playing in the Regional s.
Over the years I remember countless threads where a parent accused various teams of having illegal players and little to no action was taken against the player or school. I do not recall one lady whose playing status was impacted in SW Ohio, those that posted about the Northern Ohio ladies may have a different take.
From 2009 through 2014 we had a lot of movement of players from school to school at the varsity level within our conference or between conferences (I am sure the past few years there has been more).
If you have rental properties or, relatives etc. that are willing to allow a player to use an address you can move about pretty freely. Heck there are so many split families these days where dad lives in one district, mom in another and the grandparents in two others that kids move from school to school anyhow with nothing to do with sport...I get several students per year living in one district but registered in another with open enrollment and this is not done for sport...
I know of one lady where OHSAA made two visits to the move in players "new address" spent about 20 minuets in total talking with the parents as well as the previous schools AD and they were good to go. Even though the player never left her old address...
Chasing these situations along with the other many true or false reports keeps OHSAA busy so, I would think middle school ball would fall pretty low on the priority list...
Not to say it could not happen but for every one incident that is found to have merit there are ten or more that go untouched. Dose not make it right but it happens...