It's hard to say, as I suspect it's quite variable. If you believe the campaigning organisations like TT, the discussions by WSOH here and on Twatter, etc, the broad generalisation is that the popularity of this stuff is much higher in "less deprived" school catchments.
The Corridor of Righteous Material is something I've personally seen though. A couple of years ago at Open Day at our catchment secondary - one whole corridor festooned with the various stripy flags, handmade alphabet-soup posters with all the catchphrases and biologically-incorrect blurb and dodgy stats and kid-friendly cartoons of baked bipeds. It was startling to me, as I hadn't long been corrupted into TWSOH back then.
(We didn't pick that school, not specifically because of the Corridor I hasten to add).
I can also confirm the sudden explosion of trans identification. This did happen in my DDs' school. Year 7, within the space of a few days/weeks, several girls* declared they were trans and had new names and pronouns (mostly NB apart from one who said they were a boy). The school have gone along with the names, I don't know about the pronouns.
*Girls in the correct meaning of "juvenile human female."