Can you just clarify what age are 'High school' students. I went to secondary school from age 12-17 when I went to university.
School had a very strict uniform policy (this backfired during my time there and was relaxed) and at least, everyone looked the same and any social differences were not aparent.
Popular? We all had our friends at school and outside. It was outside school that social differences and class became aparent and there was more of a 'birds of a feather' culture.
(In later years, the school was merged with another local school and our principal dictated that we were not allowed to fraternise with the pupils from it. Didn't work for me - I've been married to one of them for 42 years!)
High school = secondary school. Ages 13-17 or 14-17, depending on the school system. Nowadays some are ages 15-17 (in school systems that have junior high, which is maybe ages 11-13?). My high school had 5 grades, 8th-12th (ages 13-17). After you finish 12th grade (you are about 17 or 18 depending on when your birthday is), you graduate from high school (get your diploma), and can enter a college or university (or whatever further education you want to pursue).