"Peoples" in the example above is right, it's just a slightly tricky grammar point. The word "people" is sometimes used to refer to "a group of people who belong to a single ethnic group or nationality." When you are using "people" in this sense of the word, it's okay to use "peoples" to mean "multiple different groups of people who belong to different ethnic groups/nationalities." http://www.learnersdictionary.com/qa/What-is-the-difference-between-people-and-peoples- I wouldn't worry too much about this particular topic. It's just a tiny peculiarity of English and it only comes up very, very rarely, and almost always in academic conversation.

"Peoples" means a group of populations. For example "the native American peoples" means the tribes that were living in America before Europeans settled it. Whereas "the American people" would mean "the group of people known as Americans (living in America)".

In this context, "peoples" would mean "separate groups of people" or "different communities".

Your teacher is correct. This usage is used in sociology, government, etc. Peoples refers to a nationality.

Thank you so much!!! :)