Lady, I agree if one believes it's an issue the suggestions youve outlined would be possible solutions.
Personally it wasn't, and isn't, a big issue for me, nor are flashes of knickers doing cartwheels.
But I can see how for schools, and the complex and ambiguous rules about underwear that exist, creates situations where they introduce rules about shorts, or those you suggest.
I don't agree with it, it's just another example do the collective insanity, but I understand how given ambiguous norms, it comes about.
So I just found the predictable, girls are being made ashamed, subjugated again, and why not just make them wear burkas, type comments, to be missing the more nuanced debate which is related to our own mad inconsistent rules about bodies and underwear.