There are still a few state secondary schools that are skirts-only - no trousers allowed! It's hard to say how many such schools there are, but there are not less than a couple of dozen in England, mostly in the south east, with many more in Ireland (both North and the Republic) where skirt-only rules are routine.
Two readers of this blog have said that the school either they (or their daughter) attend are considering changing their uniforms to ban trousers. Who knew that was still happening in this day and age?
Just to be clear, this blog is pro-choice and does not endorse skirt or trouser bans.