I found this useful guidance:
www.natre.org.uk/about-re/legal-requirements/
Including this quote:
Schools with a religious designation may prioritise one religion in their RE curriculum, but all schools must recognise diverse religions and systems of belief in the UK both locally and nationally.
Yet here we find a school teaching gender identity as fact, without any balancing teaching that many (most!) people don't believe in gender identity and that's okay too:
www.dailymail.co.uk/news/article-12752995/video-exposes-trans-indoctrination-primary-school-teacher-inclusion-lessons.html
So, should parents start challenging these breaches of secularity, or should they be insisting that gender identity teaching be confined to RE lessons (which children can be withdrawn from)?