Ever heard of peer pressure in high school? Sure you can tell your own kids to wear proper clothing. But if she has friends walking around in beach clothing and she’s not, she’s gonna be left out.

You're arguing a different issue. Remove any midriff elements from the conversation and you could be talking about the latest designer shoes or brand of jeans. So midriff specifically is immaterial to that argument. If you want an environment of uniform dress, then you're arguing for school uniforms. Arguments pro and con of school uniforms are outside of the scope of this discussion.

Board just has to state: wear what you want but see to it that it at least goes to the top of your knees and it covers your ribs.

And then we get back to the problem that the Board is trying to get away from which is educators being forced to become "fashion police". There's been historical problems with that including selective enforcement. The actions the Board are taking are specifically to let educators be educators.