How do you politely refer to a group of people with the pronoun you?

Question

Specifically, if a teacher said "I've finished grading your tests.", adressing the students, would he use あなた? I've seen it been said a couple times that あなた isn't that polite, so would the teacher use it to refer to his students? Or would he use another word?

Answer 1

In some cases, including a teacher talking to students, using あなた sounds cold, rather than non-polite. (Using あなた towards parents or teachers is considered impolite.)

A teacher can use あなたがた to students, e.g. when s/he is scolding them for some bad behavior. But in a case like the one in question, I suppose the most natural would be みなさん (or less politely and more friendlily みんな).

Using みなさん as polite plural you works broadly (e.g. in a working environment, to colleagues), but as mentioned above, whether it's ok to use あなた would be ultimately a case-by-case matter.

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For the particular sentence, not using a pronoun at all may be even more natural: テストの採点が終わりました. Who did the grading whose tests is just obvious and can/should be omitted.