We already know this: What is "cool" varies from person to person. We knew it in school. Some kids thought drugs and partying were cool; some disagreed vehemently. That's more extreme, but there are grayer shades.
Which kids in your class did you think were cool? I'm not talking jocks and cheerleaders vs. geeks and nerds. More like which cheerleader—the queen-bee who seems to have it all under control, the sweet one who seems happy all the time, the hard-working one who's all about perfecting her handsprings? (Were they all the same person in your case?)
Who we individually think is cool is entirely subjective. Collectively, though, there's generally a majority agreeing on one person/thing or another being cool.
When I'm teaching, most of my time is naturally devoted to the whole "teaching" part. Still, there are a few minutes in every class near the end where I fall into people-watching. Some students are obviously the "cool" kids (and there's usually more than one distinct set of them). Some are obviously on the outskirts of Popularity-ville. Many are somewhere in-between.
I should know better, but it still surprises me sometimes to see who some kids are (or aren't) friends with.
The whole thing is such a game. Even as adults, we don't escape it. And yet, as an adult, it twists a little.
Not all my students think I'm cool. Some don't even like me a little bit. But I can guarantee I'm "cooler" and more popular as a teacher than I ever was as a student.
The students who do think I'm cool often strike me as those who wouldn't have noticed me when I was in school.
On the flip-side ... I see those "popular" kids in a way I never could back in those days.
We're a bunch of complicated creatures, aren't we?