You CAN say : Class is finished. I am not sure what the grammar is exactly but this sounds formal to me as a native speaker. I would say : class is done/ class is over but class has ended sounds too formal to me. Nevertheless, it is still correct to say. I hope this helped :)

"finished" is a past participle ("The meal has finished / I have finished eating my food") and an adjective ("The meal is finished") As an adjective, the meaning is the same as "over". ("The meal is over") "Ended" is only a past participle in everyday language. The intransitive usages of end and finish have the same meaning - to indicate the natural or expected completion of something. ("The meal has ended" = "The meal has finished") As a transitive verb, "end" is often used in the context of stopping something from continuing e.g. I ended my relationship with my girlfriend - we weren't right for each other.

You can use finish for things. "The class has finished," would be perfectly good English. You would say 'The class has ended." With homework we would say 'I have finished (or I have done or I have completed) my homework." We would not really use 'ended,' or 'over,' with homework.