For someone considered an A-list star, Cameron Diaz' report card features plenty of Ds - 'The Green Hornet', 'Charlie's Angels: Full Throttle' and 'The Sweetest Thing' to name but three. If anyone needs to improve their average and turn in a memorable performance in a good movie it's her, but based on past results it was perfectly reasonable to view 'Bad Teacher' as 'just another Cameron Diaz comedy'.

She plays Elizabeth Halsey, a just-dumped gold digger who's forced to return to teaching in a junior high school to make ends meet. Far more concerned with expanding her own chest than the minds of her students, Halsey needs $10,000 to fund the surgery and will try every hustle and come-on she can think of to get her one day closer to silicone salvation.

Once the perfect cleavage is in place, Halsey is convinced she'll be able to snare Mr Right, and when silver spoon substitute teacher Scott Delacorte (Timberlake) walks through the doors of John Adams Middle School, she reckons she's found her man. Trouble is he's got the hots for Amy Squirrel (Punch), the goody-goody from across the hall whose measurements are just like her results - very impressive.

There are no details on whether Diaz received the script for 'Bad Teacher' with a big pink bow wrapped around it, but signing up for the movie represents one of the best moves of her career. With an arsenal of one-liners and put-downs, strong turns by the supporting cast and a willingness by the leading lady to poke fun at herself and her own ageing, 'Bad Teacher' is one for those who like their comedy black. And bitter.

Every character here is on the receiving end of some kind of humiliation, and the squirm-in-seat moments are plenty - if you're not remembering the geek horrors from your own school days, then the red cards from crushes will flash before your eyes once again. Just like former girlfriend Diaz, Timberlake takes to sending up his own hotness with great gusto here, and one fluid scene involving the two of them manages to equal her classic hair-do in 'There's Something About Mary' and guarantees you'll never look at him or hear 'Rock Your Body' in quite the same way.

We're never told what made Halsey so bad; Segel's turn as the big oaf gym teacher with the bigger heart deserved more screen time and the talents of the school kids also go to waste, but 'Bad Teacher' is an all-too-quick 90 minutes that even some of Diaz' biggest, well, knockers should appreciate. At this rate even forgetting about that sing-along in 'The Sweetest Thing' seems possible.

This summer's assessment: keep up the good work.

Harry Guerin