What we know about men's behaviour in public toilets:
In school settings some boys have and will continue to peer over the top of cubicles/underneath.
Men piss on and round seats.
Some adult men put spy cams into toilets to try to capture images of women's genitals.
Some men get off on menstruation.
Some men wank and leave semen in public toilets.
Single sex toilets do not, of course, stop girls bullying one another. They do, however, mean that girls are not exposed to the above behaviours.
Single sex toilets in schools should be utterly uncontroversial as the sensible way of organising toilet provision. And they need to be single sex, not single gender, given that school children cannot obtain GRCs therefore schools would have to function on "self ID", and as we know, under self-ID there is no way for an external observer to tell the difference between someone who genuinely believes themselves to be trans and someone taking the piss.