The general idea is that it is extremely important to be "popular" in American schools. What you have observed is correct, it's a national "obsession". I noticed the same thing when I was in my teens and read American books and watched some American films etc.

It is a bit strange, because the things that are supposed to make a pupil "popular" are very shallow. A lot of kids have other interests, are not sufficiently good looking/good at sports etc.
Last time I saw this syndrome was when I decided to watch Twilight (the film). I think the idea is that the heroine is not popular, but I might be wrong.

I had some American kids at my school (it was a marginally international school) and I remember one girl who had just arrived from the States actually asking me whether my friends and I were the "popular" group or not. I had no idea what to respond and the question was very blunt. England has something a bit similar to the US. The "popular" girls seem to be the sluttiest ones, judging from the appearance... It's such a shame that kids concern themselves with such nonsense when they should be studying! If this kind of culture has not affected Russia (yet) then that's a very good thing.