Why are mature students more cliquey and competetive?

Basically I am in my second year of a history degree. There is a group of other mature students in my lecture and seminar group, who constantly cling to each other. Their 'leader' is this 40 year old housewife who is quite pretentious and concieted. I try and be nice and work with them bt they seem to rebuff me! They-mainly the ring leader- only talk to me to catch me out or undermine my confidence (eg "I've allready thought of my dissetation next year, have you?", "my seminar tutor told me I am gifted and have a lot of potential" or my favourite "have you done this weeks reading?"[no i just mess about and watch day time TV(!)]). Maybe they think I am unintelligent/lazy and an easy target to make themselves feel better! Oh and I suspect the ring leader of colluding with her best mate (also in this group) and I am tempted to gr them up as (a) theyre gits! (b) theyve given themselves an unfair advantage!