My younger son is starting in year 7 at the same high school as my other three next month, his sisters are starting year 10 and year 11, and my older son is starting his first year of sixth form, which has the same uniform.
Their uniform has until now consisted of a sweatshirt and a choice between either polo shirt or shirt with school ties being optional. But the school has changed the uniform for September so that all those starting in year 7 must only wear polo shirts and that although older pupils still have a choice between shirts and polos, older girls should no longer wear school ties although ties are still optional for boys.
My older lad occasionally wears a polo but prefers wearing a shirt and tie, as do both girls, who want to continue to be able to do so. My youngest lad is happy to wear polos but I have also bought him some proper shirts.
If the girls continue to wear ties, they won't be visible under their sweatshirts so I don't see why girls shouldn't be able to wear them when boys can? Most pupils currently wear shirts rather than polos so why ban those for new starters too?