NOW MIGHT BE a good time to rethink your lifetime ban on comic remakes of moldering TV cop shows.

Because against all odds, "21 Jump Street" is actually pretty funny and lifts movie comedy out of its recent creative rut.

A rut that's arisen from insular, too-chummy collaborations among the usual comedy suspects. "Jump Street" shakes things up, bringing in directors Phil Lord and Christopher Miller, who directed the animated sleeper hit "Cloudy with a Chance of Meatballs," a huge crowd pleaser back in 2009.

The movie also pairs (slimmed down) Jonah Hill with a new buddy-comedy pal, Channing Tatum.

Channing Tatum? Yeah, that's what I thought. The guy has been playing earnest, muscle-bound hunks and brooding boyfriends for so long you think that's all he can do.

But Tatum shows a real talent for comedy here, and brings a fresh, "Twins Jr." chemistry to his pairing with Hill, who showed in "Moneyball" that he needed some time off from the Judd Apatow laugh factory.

Hill and Tatum play Schmidt and Jenko, old high school antagonists (Hill the nerd, Tatum the jock) who become friends at the police academy, subsidizing each other's strengths in the classroom and on the obstacle course.

They become hapless bicycle cops recruited (by Ice Cube) into an undercover unit the places cops in high schools, where they ferret out drug dealers selling dangerous psychoactive drugs.

"Jump Street" does some smart things. For one, it immediately disarms you by making pointed jokes about the creative bankruptcy of the movie industry. (Ice Cube, for instance, makes fourth-wall cracks about angry black police captains in cop-show knock-off movies) .

The movie also stands as something more than a spoof, and plays around with a couple of funny themes. The undercover cops, particularly ex-jock Jenko, finds that post-"Glee" high school culture has changed considerably.

Nerdy things are cool, like reading, theater, environmentalism, activism. In today's high school, you don't want to be the only guy who hasn't seen the Kony video. (Jenko pulls up in his gas-guzzling muscle car and immediately has to answer questions about its fuel consumption).

As a consequence, egghead Schmidt unexpectedly is invited to infiltrate the "in" kids (also the dealers), while lunkhead Jenko gets a taste of life among the social outcasts. His confusion is the source of many laughs, as is his envy of Schmidt's social success.

"Jump Street" is so buoyant and likable that you can forget what earns it an "R" rating. But it's no gross-out affair, and it's the rare contemporary comedy that doesn't chase cheap laughs.

It only becomes tiresome when it turns to action - a little more imagination in the climactic prom-night limo chase might have yielded a classic.

Even so, "Jump Street" takes most recent movie comedies to school.

Contact Gary Thompson at 215-854-5992 or thompsg@phillynews.com. Read his blog, "Keep it Reel" at www.philly.com/keepitreel.