If "同学们好！" means "Hello classmates!", can also a teacher say that to its students, despite the fact that the teacher is essentially not a classmate / not part of the student group?
I ask this because my Chinese textbook suggests that a teacher could say this. So I am a bit confused now.
When a teacher or any outsider says 同学们, 同学 is referred to as a "student"
Example:
张同学，李同学 = classmate Zhang, classmate Li (from a classmate's standpoint, but it is too formal, typically classmates just address each other with their full names)
张同学，李同学 = student Zhang, student Li (from a teacher or any outsider's standpoint)
同学们好 = "hello students" or "hello class"
In China School, before teaching, always say: Teacher: 同学们好！ Students: 老师好！
teacher is not part of the student group
同学 has two meanings: 1 classmate 2 student
So a teacher can definitely say 同学们, which means students. A teacher can also say **同学, which means student **.
"同学" shows a special relationship between you and the student. If you are a student, it means you are classmates, schoolmates,etc. If you are a teacher, it shows you teach them.
However, you can always use it to shorten the distance between you and the person you refer.
