My memo to the makers of this sloppily written and totally annoying 92 minutes of slap-dash filmmaking would be have the courage of your convictions to follow through and not be a tease that never delivers on your promise.

Despite the lure of something nasty, cutting and raunchy the finished product has no edge and is unwilling to push the envelope

The concept is ripe with possibility - an oversexed, drug-abusing, foul-mouthed, couldn’t-care-less woman put in charge of a classroom - but the result is obvious, tedious and disappointing.

If Bad Santa is the template, Bad Teacher wants to be naughty but not naughty enough to shock viewers. Bad Santa on the hand took no prisoners and made no excuses with convenient change of heart for Billy Bob Thornton’s nasty, unrepentant character who ultimately is more appealing then Cameron Diaz’s obnoxious caricature.

It’s an open question why anyone would hire Elizabeth Halsey (Diaz) to teach junior high without a word of any qualifications, but we’re supposed to blindly accept the premise that nobody is noticing the worst teacher in the world’s shortcomings except her odd goody-two-shoes co-worker Amy Squirrel (Lucy Punch).

The reason Elizabeth needs a job is because her ex-fiancé figured out that she’s a gold-digger and cancelled the wedding.

Her reaction is to seek out a new money tree and, as a means of enhancing her appeal to achieve that end, she has decided to get a boob job.

But finding the spare $10,000 to achieve her goal is proving difficult, but hope soon walks through the door in the form of geeky substitute teacher Scott Delacorte (Justin Timberlake), whose family is rich.

Problem is that she has a rival for Mister Milquetoast and before you know it Amy and Scott are dating.

All this time she ignores the advances of gym teacher Russell Gettis (Jason Segel), who is so obviously a better match for her but is lacking Scott‘s monetary assets.

Apart from some isolated scenes that work, including a car wash sequence and Elizabeth’s unusual dodge ball-derived punishment-reward system, the comedy is obvious, laboured and tepid but even this is more acceptable than the mind-bogglingly unrewarding, stupefyingly annoying ending which basically doesn’t make a whole lot of sense.

The supposed thrill of watching Cameron Diaz playing against type wears off pretty quickly because her character is basically unlikable, yet you just know a turnaround is down the track because the creative team refuses to make her a complete witch. Her unconvincing foul-mouthed nymphomaniac is not the stuff of true black comedy.

Apart from the always agreeable Jason Segal, who emerges mostly unscathed as the as the only ‘normal’ character, the solid support cast is lumbered with cartoonish personas the equal of Elizabeth.

Lucy Punch’s is probably next best but Amy isn’t much more than the typical goody two-shoes whose sunny exterior hides an interior ugliness, Scott is a teenager in an adult’s body and John Michael Higgins’ Principal Snur is an obtuse moron with a dolphin fetish.

Ultimately this is another Hollywood missed opportunity. I can see it finding an audience among the masses programmed to accept a few four-letter words, a fart joke and some dry humping as the pinnacle of hilarious raunchy cinema.

Trouble is it needs believable characters and decent non-scattershot screenplay and a willingness to shock to really gp through with the job properly.

Rating: 2

This is the start of a new rating

system for me which will now be

out of a maximum five not 10.

Now screening at Reading Cinemas