I use fx_cast extension, it's been working great for years. Although it needs the "bridge" to be installed, which is some minimal headless chromium thing.

It's not a seemless experience, as it has a domain whitelist enabled by default, so you need to mess with it in the extension settings first, but once it's been set up, it's fine.

Sometimes it can mix up old/expired sessions, so the website would say you're casting but you're not. You can just press the "active" cast button and disconnect, then reconnect again.

Some other times (rarely) it fails to mock the casting feature and you won't see the cast button or it would be disabled. Refreshing the page helps. If not, double check your whitelist.

600 students, ~100 teachers, everyone has an iPad (plus many have an iPhone). ~20 students per class.

AirPlay often didn't work with the 'smart' boards, and not even much better with the extra AppleTVs we got.
AirDrop only showed ~50% of the students, of course including ones in other classrooms, so that isn't due to distance. Even if you were displayed, again 50% that the file actually got to you. A restart 'fixed' that - but restarting every 1.5 hours for a new class because Apples AirDrop team is apparently just as incompetent as its MDM team is pretty annoying. Then, sometimes, WiFi was way too unstable, but still used by AirDrop normally, which meant nothing worked.

We resorted to teams, which was perfect for me, as I was using a laptop at that point, as it was much better suited for basically everything done in class.

It may work in small groups, eg. one to one, but only if both have an Apple device, which isn't really likely. And in larger groups, eg. schools, it scales very badly.

Edit: I forgot to say: I have a literal tirade about apple devices, in that context and in general, but that's only minorly relevant, and I'm too lazy to translate it to english.

Android users use quick share these days

Couldn't you just do that with Bluetooth like 20 years ago?