Well done for voicing your disagreement Dinosaurhearmeroar, that cannot have been easy to do in the current climate. I just wanted to point out that this:
we are getting 12 year olds requesting name changes and we simply go along with it due to it being a protected characteristic.
is a complete misunderstanding of the protected characteristic of gender reassignment and how it works.
It most definitely does not mean socially transitioning these girls without their parents knowledge or consent, as that may be a violation of these children's rights under the UN Convention on the Rights of the Child as well as a breach of safeguarding rules and a big fucking no for child protection.
For starters, and to protect yourself, if any of these girls disclose to you that they want to socially transition in the future, do not promise to keep that a secret to the girl in question, then log it as a safeguarding concern (highlighting the very high co-morbidity of mental health issues and trauma in children diagnosed with gender dysphoria and the fact that trans rights organisations claim unequivocally that children who are not supported by their parents have worse outcomes than those who do), then pass this on to your safeguarding lead at school. No matter who that is.
If the safeguarding lead decides not to act on your concerns, that is their decision, not yours.
As for how the protected characteristic of gender reassignment works, it means that if a girl comes to you saying she identifies as a boy, there's two things you must not do:
You must not exclude her from any activities that you put on for girls because she no longer identifies as a girl. (That's because you cannot treat a female pupil differently to all other female pupil because they no longer identify as girls. That would be discrimination on the basis of sex.)
You must not force her to take part in any activities that you put on for girls, because she no longer identifies as one. (That's because you must make reasonable adjustments for someone who identifies as trans if they request it. To do otherwise would be discrimination on the basis of gender reassignment.)
In a mixed-sex school this would also apply to single-sex facilities. (So you should not exclude such a girl from facilities provided for her own sex and you should not force her to use the facilities provided for her own sex. Instead the EHRC recommends the provision of an alternative facility, but only if the girl does not wish to use the facilities provided for her own sex.)
I'm not sure how your school handles facilities, since the whole school is just for girls, but if you provide a different one for girls who identify as trans, you should not tell them they have to use it.
Otherwise I would also recommend reading those resources mentioned by PP.