Mean Girls (2004)

A bit of fluff that pushed Lindsay Lohan even further towards her current teen queen status.  She plays a 16-year old that was home-schooled by her folks when they lived in Africa but who goes to regular school for the first time when they return to the States.  She is an innocent in a lion's den but soon learns to differentiate between the nerds, the jocks, the weirdos and the "plastics" (the female in-crowd led by the self-serving Rachel McAdams).  When she takes up with the latter group she finds herself changing for the worse and tries to undermine the McAdams character and to steal her boyfriend.  While possibly marginally more sharply written than your average teen comedy, it was all still fairly formulaic stuff and naturally they are all far far better people by the end of the movie.