I might be particularly cliché hating, but I think everyone agrees when I say that this is TOO much. As Billina and RoxStar said, it's just so done already. It's like an American Pie or Not Another Teenage Movie script - and those movies are parodies over high school stereotypes. So unless you are writing a satire or a parody, this is quite bad, character wise.
Now, my advice is take a bowl, scribble down all the character traits you have here, like "pregnant teen", "british", "likes mythology", "shy", "cheerleader", "fashionista", "mean", "a bit stupid" and so on, on little notes, throw them in the bowl, shake the bowl so they get all mixed up, then you assign all your characters new traits. Why can't the cute boy be a teenage father? Or the cheerleader a fan of mythology? Or the shy, mousy girl a Brit? Or the teen age mother a fashionista?
So, that's my first point - skip the old stereotypes because they are lame.
My other points are not as big, but still: skip the condemning, judgemental tone, like "People magazine is sleazy", "I don't consider Bethany a slut when she sleeps with a lot of guys" (even if she DOESN'T consider Bethany a slut, she is hinting that sleeping with a lot of guys makes you slut), "Two teenagers defiantly couldn’t take care of a baby by themselves", and so on. First of all, People mag may or may not be sleazy, but you sound so damn judgemental in that sentence, like anyone who reads it are idiots. It makes Kristie just as mean as Geanie, who thinks people who don't wear skirts are lesbians. Sleeping with lots of guys makes you a person who sleeps with a lot of guys. Not more, not less. Same with teenage parents. Are you writing a fictional novel or a political newsletter? Stop putting all your own values into this text, it sounds very judgemental.
And yes, Kristie sounds both quite judgemental and very mean to Bethany. Calling someone a bitch is quite harsh. Let Kristie and Bethany be nicer to each other. It will make both characters more likeable.
So far, none of the characters are really likeable, but except from that, I don't have that much to complain about. I liked how the dialogue carried the text forward and gave you an idea of the place. That was really good. So, no problem with that. Keep writing, it'll get better!