'Bad Teacher' could use more class

In the strenuously R-rated comedy "Bad Teacher," Cameron Diaz plays the title role of Elizabeth Halsey, whose idea of shaping young minds is to shove a DVD in the player and finish off that mini-bottle of Jim Beam.

She joins a long line of movie reprobates, including Walter Matthau's slovenly Little League coach in "The Bad News Bears" and Billy Bob Thornton's alcoholic thief in "Bad Santa," but she's unusual for being a woman. Diaz's character tries to break into this comedic boys' club, but gender isn't the only thing holding her back.

A blatant gold-digger, Halsey is teaching at John Adams Middle School only to pay for the breast implants she'll need to land a wealthy whale. Enter new teacher Scott Delacorte (Justin Timberlake), a pudding-headed nerd with family money; he'll do. But Elizabeth not only faces unexpected competition from chipper co-worker Amy Squirrel (Lucy Punch, "Dinner for Schmucks"), she finds herself enjoying the never-ending overtures of doughy gym teacher Russell Gettis (Jason Segel).

Despite the haphazard plot (a state test, a cash bonus, a purloined answer-key), the cast manages to shine; Diaz and Segel make an appealingly rascally pair. But the movie tries so hard to deliver on its title that it gives Elizabeth few redeeming qualities. Her manipulative sexuality makes her seem more like a sociopath than a lovable rogue.

Is this a double standard? Perhaps so, given that the men of "The Hangover Part II" remain America's sweethearts even after sleeping with hookers and mistreating animals. The problem with "Bad Teacher" is not that its heroine is a woman but one without a heart.