Mine didn't really get cliquey until sixth form. Before then everyone just had different mates and then depending on which classes you had you'd have a different set of mates.

At sixth form the whole year got decimated to maybe 50 people, and some of smaller friendship groups merged into one or two groups depending on who had a car or was throwing a house party. There was some specialization: math/science/computer nerds, clear jock group, future fascists, and everyone else.

Like a lot of people, I pretty much just orbited around the different groups (not the jocks and fascists though)