The key problem with Bad Teacher is, well, that she's not really all that bad is she? This is a classic example of a comedy never pushing itself enough in the direction it really deserves to go. Jake Kasdan's comedy has flashes of something more, something funnier or riskier, but it never quite has the balls to really go there - as a result the whole thing is underheated, eventually pandering to the need for a touch of humanity in a character that should have remained a truly reprehensible human being.

Cameron Diaz, you see, is damn good with what she's given; her irresponsible teacher on her quest for big tits comes across as an utterly amoral, loathsome, opportunistic bitch for much of this and Diaz is clearly loving every minute of it. The trouble is, she's a miscalculation - just why she does what she does is never mined beyond the threadbare, making it hard to latch onto her villainy, and though Kasdan doesn't let a sappy Hollywood comedy ending completely infect this, her budding romance with Jason Segel's laid back gym teacher does reveal a better side to her character I never wanted to see. Segel is barely a character at all infact, better served are Justin Timberlake (playing an effete, two-faced substitute teacher decently) and Lucy Punch, who steals the show almost as a horrifically irritating fellow do-gooding teacher, a good foil to Diaz's overt bitchiness.

But ultimately, it's just not that funny - and that's where it falls down. I laughed out loud about four times and, sorry, that ain't enough - not when you've got scenarios and a general idea that actually has a great deal of fertile comic potential. I work in a school and, believe me, they can be hilarious places to work. Bad Teacher doesn't reflect that nearly enough.