Oh FFS. I'm actually a firm believer in 'gender-neutral' uniform policies. I don't think there's any good reason why boys and girls should have to wear different clothes.
But 'gender-neutral' doesn't have to mean all children wear trousers. It can mean presenting the options and letting the child choose.
My girls are only primary age, but they have always chosen to wear skirts and dresses and find them comfortable and practical. They rarely wear trousers, even outside school. My youngest is incredibly slim, so getting trousers to fit can be an issue.
Don't force girls to wear trousers, just let everybody choose.