You will get the occasional unicorn who is liked universally, but most populars in school are in cliques with the other populars and they emphasize their status by making sure everyone else knows where they land on the foodchain, especially the unpopulars.
Anyway most of these bullying incidents sound pretty normal for school - laughing at a bottle cap being flicked at someone, telling a kid at lunch that he eats too much, being jealous about another girl hanging out with handsome guys. The SJ one - if true - is more extreme, but a lot of kids are dicks at school but still manage to develop into decent adults. These incidents sound like a tame day when I was at school, and we didn't have a hyper competitive environment and parents expecting their kids to network upwards only. Last year I read an article about a Seoul mother who told her daughter she needed to slap lower status classmates so they would knew she was superior to them. It's on a different level there. We should remember that.