Trans pupils and dorms in France

I don't want to worry you, OP, this is a tough situation.

Helping your daughter draw strong boundaries is great advice; but my concern would be as much for consensual activity as anything else.

How on earth does anyone think having mixed sex dorms for teenagers is going to work?!

Are other parents aware of this situation?

Most of these children are highly vulnerable. The problems arise with the emotional manipulation that's encouraged by others in getting their perceived demands met. That's where it's a problem in what should be single sex spaces - especially sleeping and washing with sometimes limited and unaware supervision.
If there's no alternative then enabling her to have firm boundaries and to seek support from you instantly if she has any sense of her boundaries being challenged is critical. Especially if she's a new student which can make her more vulnerable with (hopefully for a while) a more limited peer support group.
Is there any possibility of a similar course you'd deem acceptable somewhere where she doesn't have to board in a school boasting of eroding boundaries for girls?

Could you drive her there and back if it’s an hour away if she was ever put in a situation where she was boarding with a boy?

Count yourself lucky that you’ve been given an early warning. Read ‘Lost in Trans Nation’ book by Miriam Grossman, ‘Trans’ by Helen Joyce or ‘Time to Think’ by Hannah Barnes, so that you’re well informed. There is also a movie ‘War on Children’ by Robby Starbuck.

Cross post with OP

Yeah, I’d not be giving them my money tbh.

I suspect that this is a state secondary school where children have to board during the week because travelling distances are too great to get to and from school every day, but the OP can confirm whether this is true or not.

While few countries have great records of safeguarding children, France seems to have a greater problem than most with the sexual assault of girls. There's been a series of recent reports, scandals exposing paedophilia, incest and the routine abuse of girls. This was in the Times the other day about the film industry:

https://www.thetimes.co.uk/article/d84680fd-e3d2-489c-aaa9-1e4db7a6f68d?shareToken=c3ef9d31deea54f37b9fddae9f100dd4

& this from several years back in the Guardian:

https://www.theguardian.com/books/2021/feb/25/memoirs-writers-highlight-sexual-abuse-in-france-metoo

Does she have to board in France? Are these independent schools OP?

I'd rule that one out and look at the other schools. It might not be illegal to house boys and girls together but you might find a school where it's not so actively encouraged.

OP if your daughter has to board and that's the policy and you don't want to protest or be seen as "anti trans', pretty much the only thing you can do is make sure your daughter has very strong boundaries about people seeing her body and various kinds of sexual contact, whatever the gender identity of those around her

Not easy, I would imagine, what with peer pressure and general French culture (I used to live in France).

Well they’ll be going through puberty now so it’ll be blindingly obvious who’s a real girl and who isn’t. So if DD suspects a dormmate is a boy masquerading as female she needs to ask to move. If you aren’t brave enough to say why then make up another reason. I’d have no qualms about telling them why though. Presumably there’s every chance she’ll be playing sports and expected to change infront of boys too if they want to play dress up. Yeah, I’d not be giving them my money tbh.

I would not be happy about this. The school has a statutory and legal responsibility to keep your child safe. Sharing a dorm with a male with a penis risks her safety.
You could enquire about their safeguarding policy and if it is missing a section on female pupils sharing intimate spaces with biological males I wound query this. You could also ask to see their risk assessment. If they don’t have these things you have every right to expect them to get them in place pronto.