Cameron Diaz and Justin Timberlake star in Columbia Pictures’ comedy “Bad Teacher.”
Justin Timberlake dry-humps Cameron Diaz while both are fully clothed in a bizarre scene that serves as a fairly convenient metaphor for the whole of “Bad Teacher” — a fitfully amusing comedy that promises far more outrageousness than it actually delivers.
Sure, Diaz swears up a storm, smokes pot, steals test scores and spends far too much time zoning out while her students are watching movies.
But she’s nowhere near as transgressive as the hero of this movie’s apparent model, Billy Bob Thornton in “Bad Santa.”
Yes, Diaz deserves credit for trying to leave behind her basically sweet persona, in a role that sort of acknowledges that even with a still-hot bod, she’s pushing 40.
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She doesn’t get nearly enough help, though.
The sloppy direction is by Jake Kasdan (“Walk Hard: The Dewey Cox Story”), and the scattershot script is by Gene Stupnitsky and Lee Eisenberg (TV’s “The Office”).
Diaz’s character hates kids, hates teaching and is engaged to a rich guy who will enable her to retire.
When that plan falls apart, she sets her sights anew on Timberlake, a milquetoast millionaire who has just joined the staff as a substitute.
Our heroine decides she needs a new pair of breasts to entice Timberlake, not easily procured on her teacher’s salary.
She solicits cash from parents for “private tutoring and skims cash from the student car wash — where she pumps up business in Daisy Dukes.
She even seduces a state official (Thomas Lennon) to procure test answers in advance (while posing as a reporter) in order to collect a cash teaching award.
Though Diaz talks dirty, this sequence turns out to be rather chaste.
Did the star or filmmakers decide they didn’t want to go as raunchy as “Bridesmaids?” — or even “There’s Something About Mary,” which Diaz made 16 years ago?
Or does the relatively brief running time suggest the studio got cold feet in the cutting room?
Certainly, “Bad Teacher” makes surprisingly little use of Timberlake’s talent for self-deprecation.
Jason Segal, who shares co-star billing with Diaz and Timberlake, also has remarkably little footage — less than Phyllis Smith as a plump, shy colleague who Diaz improbably befriends.
But he makes the most of his role as a schlubby gym teacher who sees Diaz for exactly the opportunist she is — and loves her anyway.
Diaz’s best scenes are with him and the kids, who she puts down mercilessly until she uncharacteristically takes pity on one young misfit.
Most of the laughs are collected by Lucy Punch as chirpy, borderline-psychotic teacher named Squirrel.
Timberlake initially prefers her to Diaz, but once Diaz starts moving in on him, Punch’s character starts reporting her bad behavior to the timid principal (John Michael Higgins).
Then Punch escalates her war against Diaz — pretty much making the main character in “Bad Teacher” look like Mother Teresa by comparison and stealing what little movie there is worth stealing.
lou.lumenick@nypost.com