반 ~ class, group (focus on people)
같은 반에서 처음 만났어요 ~ we first met (when we were) in the same class
우리 반은 커피숍에 갔어요 ~ we went to a cafe with our class(mates)
수업 ~ lesson/class (focus on subject that is taught)
수업 후에 집에 가요 ~ after class I’m going home.
계급 ~ (social) class