I dunno, clo.
Not sure I would want things like that in schools as if everything they represent is invincible truth.
I think a lot of conservative parents will think those flags are political and so they will feel their kids should not be subject to what they see as indoctrination.
Is there a flag for the value of accumulating knowledge, which is what a school is primarily about?
I'm more for leaving kids alone to figure things like sexuality out for themselves, and then to support them if they ask for it. But by all means, be inclusive and not pejorative.