But removing the person from the reality of their sex and reinforcing the idea that this is possible and preferable is so damaging.
Absolutely. When I think back to the time that my daughter was actively gender questioning and said she didn't know if she wanted to be a girl, she said she was thinking about "they/them" but leaning towards "he/him" and hadn't decided yet. I told her that I fully supported her exploring her thoughts on all of this but that she could not take any steps that removed her away from the reality of being a female until the end of this exploration, including stating any change in preferred pronouns.
Slowly, over time, she becoming used to the reality of her body. She still hates her breasts (uses sports bras to flatten them) and still hates periods (only gets them occasionally, owing to being on the mini-pill) but the important thing is that she understands that she is biologically female and that this can never be changed. She also understands that preferred pronouns are controversial and that although she uses these herself for trans-identifying children that she knows, not everyone does - including me. She knows that instead I avoid using any third person pronouns in such situations.
She is often mistaken as a boy. I asked her recently how this made her feel. I did so with a deliberately leading question: "I think you quite like being mistaken for a boy. Is that right?". She said yes, it's great. I just smile at people and say "No, I'm a girl. I've just got short hair and I wear boys' clothes" 👏👏 We've talked quite a bit about how it's a shame that people seem to have forgotten that girls can have short hair. It's activism like that being peddled by this PHSE provider that is driving this.
Actually, she doesn't always like being mistaken for a boy. Until very recently she wouldn't go into the ladies' loos in public places without air cover from me because she didn't like the weird looks she got. Also she still gets panic-stricken at airports when she's selected for a security pat-down and a bloke starts walking towards her. I get a very frantic "Mum... explain!". So I do. I say very matter of factly that she's a girl and I ask for the female security guard to check her. The security guards get sheepish and apologise but I smile and say it's really not a problem.
For context we're over 4 years on from when this journey started, just after she turned 13. The school and I were at odds on how to support her the whole time, meaning that they managed me as a safeguarding risk to her. That's too much of a derail for this thread but suffice to say it's been a hideous rollercoaster and I'm glad she's no longer there.Thankfully the DSL at her college has a very different take on things.
The key point being that professionals in schools (and wider support networks e.g. mental health) need a full understanding of what social transition means and why it's not a neutral act. Without this, they'll be at risk of bringing in providers such as this one.