Well, I finished secondary school past year, and I have to say that cliques don't really exist. While it's true that there were some groups of friends that always hanged out and the like, but there were not any group were you were not allowed to be. They existed because of affinities, just that. But I feel that I have to point out that male groups lasted years, while female ones didn't last long.
The people that formed the nearest things to a clique were a kind of "I'm better than the rest of the society" people, so they hanged out with few people just to feel that their group was more exclusive, while, in fact, their members weren't even close friends. In all this groups thing, I was the one who could hang out with any of them, but, at the same time, I wasn't very close with any, I just didn't have common interests with any, and the topics of conversation were boring in th elong term. Anyway I can recall a kind of group which I never hanged out with: the kind of people that just drink and try to appear that do cool stuff, I found them as the least interesting people.
But, I have to say that the effects of media caused a wannabe "popular" clique to appear within my classmates while we just started the secondary school. Nobody liked them, and nobody cared too much, but for some reason hat group was like the main one in the classroom. Maybe it was just because nobody else wanted to be the center of the attention.
I have found that media has a really important power to influence many aspects of a person and the way he relates to other ones, even affecting the way a person speaks (read below).
Additional information: I live in Argentina, we speak Spanish here, but we have a particular way of speaking: most of our verb conjuations differ in the stressing and sometimes the pronoun we use to speak. The media that influences us, if it doesn't come form the local community, usually has a classical Spanish accent. I have to say that it is really irritating to hear a child who speakis in an Spanish tone, because it means that he has been watching a lot of television, without human contact.
While I don't care about regional use of certain words (like can or tin in English), I find the Spanish accent in our country to be a way of loosing our own culture and letting the media to brainwash our population.
Diclaimer: it's all ok with Spain and it's inhabitants (really, I'm not a xenophobe by any means), I just don't like children here speaking like if they had been born there, not because of the culture, but because of the brainwashing.