Is it the kids? is it the (lack of) discipline? is it because of social reasons?
I went to public schools in different ditricts in France, and it changes a lot... It's not surprising that a school in a more urban and "bourgeois" place has more emphasis on scolar success which makes it a little easier for geeky types, but there certainly are other kinds of bullying (sometimes more on social aspects).
Of course kids at this age are very "mimetic": they want to be in the mass and do like popular ones, they suffer to be different. But they are building their personnalities: maybe they not only need better models, but also better structures to make them more mature. We're hearing about current "let-it go" public schools or about old-style strict schools, but what about making schools really more participatively democratic places to live in (I'm thinking of taking some good points from experiences like SummerHill [http://en.wikipedia.org/wiki/Summerhill_School]: I wonder what good/bad lessons we can get from that)?
I'm just thinking of this two simplistic things as I read people saying things like "lookily i was in a private school...", but school is the manufacture of future society: we should care!