I realise that this is NOT the main concern for any of us really, but what strikes me is that this is unfair to all of our children, although of girls are (as always) disproportionately at risk.
Last year at school my son was accused of something very serious, but which he did not do (school staff witnessed what actually did happen so were able to handle it very coolly) but the girl's parents backed her so fully that they reported my son to any person in authority they could possibly think of, including the police and social services.
Now - they were 7 at the time. And there were two adult witnesses who saw that this girl told a silly 7 year old fib which then got blown up out of all proportion by her parents (who believed their daughter as we all instinctively would but then refused to hear the reality).
But it chills me utterly to think what if he'd been 15/16/17/18, and in a bathroom with girls as young as 11. What if one of them made a similar claim, where there are not going to be adult witnesses around? Who is protecting any of the children in that scenario?
Girls and boys/women and men have single sex spaces for REASONS. Those reasons do not cease to exist because TRANS. I have a son and a daughter and I'm always walking the line between the two. This is a terrible terrible step backwards for girls, but also for boys, who also have a right to dignity and privacy.