I quite like that I can go to a friends house (and vice versa) and have their AirPlay speaker or TV just show up as a device to stream to. Seems a bit extreme of Rachel to call this usecase “insanity”.
The school can put them on separate networks, or they can name the devices so it's clear what room they correspond to. I'm just not seeing the problem here.
I'm assuming the school puts the devices on a network that students can't connect to, that's just a table-stakes sane thing to do.