Senior
The highest possible rank in the high school hierarchy. Fourth years are the best of the best - they've survived three years of being mocked by the grades above them and are determined to make the three years below them suffer the same way. They've got power, connections, sometimes weed, and a shitload of exams coming their way, which they'll likely either completely ace or completely fail.
Guy 1, pointing at another guy: Who's that?

Guy 2: That's a senior. I don't remember his name, but we should bow while he walks by or he'll get his connections to murder us.

Guy 1: Oh shit.