It takes an inordinate amount of time for Step Up to get to its presumed raison d’etre—the dancing. Before the climactic number, which resolves all the tortured plot issues, you have to sit through an awful lot of scenes of its porno-named hero, Tyler Gage (Channing Tatum), struggling with the dance rehearsals he must endure as part of the community-service duty he performs as penance for vandalizing a performing-arts school’s property. Student Nora (Jenna Dewan) has enlisted him as her partner in the all-important senior project which could propel her into the dance career she desperately craves.

What’s particularly dismaying here is the fact that director Anne Fletcher is also a choreographer (Bring It On, Ice Princess, Down with Love), which makes the short shrift given the dance scenes and their lack of excitement a real puzzlement. We’re teased with shots of Tyler goofing around with his buddies and little sister, as well as a very cheesy-looking pas de deux with Nora, shot through sunbeams on a deserted pier, but the final big set-piece just lays there on the screen, a welter of clichéd moves and ho-hum Muzak. To her credit, Fletcher doesn’t indulge in as much choppy MTV editing as most current dance-driven films; you actually get to see Tatum complete a move in full figure occasionally. But Fletcher shows no real talent for the dramatic scenes, be it those between Nora and her dance-disapproving, college-obsessed mom (Deirdre Lovejoy) or Tyler and his ne’er-do-well buddies, who pass the time stealing cars off the streets of Baltimore. Rachel Griffiths basically earns a paycheck as the school’s “concerned” director.

In real life, former Abercrombie & Fitch model Tatum possesses martial-arts skills which fluidly translate into some of the movie’s more exciting hip-hop moves, heavy on limb isolations. He also has an appealing soft-spoken, sensitive-brute quality which should register well with pre-teen hearts. Dewan’s character doesn’t come across as strongly, and she’s not helped by a hoochie-mama wardrobe that’s like an R-rated take on Jennifer Beale’s Flashdance rags: heavy on high heels worn with breast-emphasizing rehearsal togs. The stars’ respective posses, consisting of African-American actors who mostly cluck their disapproval or approbation from the sidelines, are competently drawn by R&B stars Mario and Heavy D, Damaine Radcliff, Drew Sidora, and De’Shawn Washington, who meets one of those tragic ghetto ends which have been an essential part of urban musicals like this since Saturday Night Fever.