Americanisms in "Cliques"

Hello everyone.

OK, so the Americanisms in this episode were not particularly important
to the story, but they got me curious. All schools across the world are
full of similar cliques, but the names of them vary wildly, even within a
country. Obviously skaters and goths are well known...

But just what are

- preppies ?
- posers ?
- jocks ?

Answers on a usenet post, please :-)

Cheers,

Brett