It seems the school governors and the headmistress genuinely believe they've had a eureka moment. I wonder why they've not paused to wonder why no other school has felt it necessary to 'protect girls' modesty' in this way? Girls are perfectly well able to protect their own modesty with the range of clothes available to them, if that's what they want (and in some cases that I see, I doubt very much that's what they want).
What a hare-brained scheme.