In Japan it seems especially difficult to pinpoint.
When I walk onto the school oval during sports activities. A single designated student shouts out some Japanese command akin to "Oi! Teacher just walked onto the sports oval! Attention!".
The message is relayed all the way to the back of the sports field. ALL students stop what they're doing even if in the middle of a game, or even if in the middle of taking a swing with the baseball bat.
They all turn to face the teacher, and on command from the designated student say "Hello Jay!", and all bow in unison. An entire oval full of students. All bowing to a single teacher that walked in. Not just me. Any teacher.
I guess, I bow back now? Ok, yes, that feels right. I'll bow. But please just carry on with your activities! So funny!
Or there's the situation where a student wants to come into the teachers' office for some reason. She has to knock, stand at the entrance, state methodically: 'Sorry for the intrusion', Name. Grade. Class. Purpose of visit. Permission to enter? Await reply from a teacher. Enter. And greet and bow any teacher you happen to pass on your way to the desk. Then apology and bow to the room in general before leaving.
Any student who makes a mistake in this regimen is usually pulled up by a teacher & made to do it again.
Teachers in Japan also play a disciplinary role. Since the working hours are crazy, and the school hours are crazier still. Often students don't see their parents many hours of the day, so a lot of life skills are left to teachers. So yeah, teachers in Japan really really can yell at their students if they do something wrong. They're pulled up for a crooked collar, or an untucked shirt. Anything which indicates a student is lacking respect is usually pulled up.
If you think about how you hold yourself when you go for a job interview, you might start to get an idea of Japanese culture. Whenever the situation is NOT casual (i.e with a bunch of friends), you should conduct yourself as professionally and as polite as you can to the situation. This concept is enforced in schools and it may be a very big reason why Japanese come across as so polite. Is it really respect? Or is it simply an upbringing of good discipline? Interesting thought!
Picture from school newsletter of opening ceremony all students shouting as loud as they could.
An English class. Usually about <35 students in a classroom. Very rarely any problems controlling them.