I don't care which one I use, I just use the one that's least likely to result in an awkward situation/people getting mad.
I'd be happy with a cis-female/other bathroom dichotomy, if everyone was cool with it. Sort people by astrological signs, I honestly don't freaking care, I just have to go to the bathroom, and it sucks constantly worrying about it.
The whole thing is miserable even for adults, I can't imagine the hell school-age transgenders go through.
It's like, okay, I'm presenting female, I either stroll into the male bathroom with a bunch of dudes glaring at me, or into the female bathroom and risk pissing off the dudes if they see me go in, and the less likely, but still possible condition of offending/disturbing the women in the women's bathroom.
Fortunately I have a semi-safe bathroom at work, but most are not so lucky. Especially the school kids.
And, honestly, WTF do guys think goes on in the women's restroom, that anyone would even want to be a voyeur to? As if women are all in there having a pajama party or something. They go in there, they use a stall, they wash their hands, and they leave. Just like the men's room, only without urinals.