Schools have a responsibility to safeguard ALL children and not to discriminate against any protected characteristic.
Using wrong sex pronouns and forcing girls (and boys) into mixed sex spaces is discriminating on the basis of protected characteristics of sex, religion and probably disability also.
Teaching children that they must lie if adults tell them to is a safeguarding failure. Teaching children that the normal rules of grammar can be bent for some people and not others is confusing at best. That third person pronouns are sometimes based on observable sex but sometimes on what - inner feelings? How are they supposed to tell, what are the rules around this? How do they know? It's all immensely destabilising for education.
If I were a teacher I'd point this out and say I would be happy to use names and not use any sex-based pronouns at all for specific children with issues around gender identity, but that I will not create a climate of fear and compelled speech against normal English usage for GC, religious, non NT, SEND, or non-native English speaking children. And that I believed using preferred pronouns is in breach of KCSIE and the existing guidance requiring teachers to be politically impartial. And goes against what Cass says too.
Sooner or later there will be lawsuits against schools. It won't be against individual teachers, but it will be against schools and the Head, ultimately, will be responsible I suppose.
I very much hope there will be more EHCPs which safeguard against this political ideology too.
Teachers, and schools, will have to manage a diversity of opinion and belief. They manage it for different religious beliefs already, how this one ideology has caused such total capitulation is really quite frightening.