It was reported that a school banned children from wearing frilly socks for health and safety reasons.
There is nothing in health and safety law which stipulates how long or short frills on school girls' socks should be. These socks are unlikely to be a serious hazard unless they are torn and trailing on the floor.
If you tried to ban everything children could trip over, they wouldn't be able to do anything.
Schools are free to set their own uniform policies but these decisions shouldn't hide behind spurious references to health and safety law.