Have already run a residential school trip with a trans pupil who shared bathrooms with others of the new gender. This was in accommodation with separate toilets and showers within a male and a female bathroom so only sinks were communal, and these were in bedrooms too. All rooms were single.
However, we did all the research and contacted the (Scottish) council and, yes, the pupil could use the bathroom of their choice and sleep in rooms amongst other boys. The trip was to England so not sure how that would have worked. All pupils aged 15-18.
I only went along with it because of the single rooms and because the pupil is FTM so not a physical threat but I did feel that boys might have objected (they didn’t) or parents. Imagine if there had been a “gay” relationship as a result (said pupil is now a gay male) that had ended with pregnancy!
I know most concerns are with MTF because of issues of violence / rape but this was a risk too.
And, no, we were not required to put it in our risk assessment because “he” was no more a risk than any other boys (nor at greater risk in spite of the oft repeated suicide risk that led to the changes).