Really there’s no way to test that a boy is ‘bad’ enough to play with the girls, so I simply wouldn’t allow it.
I could see a case made for the freakish girl who’s good enough to play on the boys team, when there’s no equivalent team for her. After all, she can try out and make it or not make it just like any of the boys.
But that asymmetry is problematic, so I’d understand scratching that too.
—After all, she can try out and make it or not make it just like any of the boys.—
Though I consider it a “camel’s nose” issue, that might be a good way to do it.
The problem is that if you do it across the board (good girl plays with boys and bad boy plays with girls, you end up with one of those “rose by any name” scenarios:
You end up with the “good team” (which is mostly boys) and the “bad team” (which is mostly girls). I’m not sure how people would react to that.