BY ROGER MOORE

McCLATCHY-TRIBUNE NEWS SERVICE

It's funny how the beloved movies of one's less politically correct youth turn out to have a lot more edge to them once you show them to your own kids.

"Back to the Future" has more sexuality than you remember, and little blasts of profanity. "Adventures in Babysitting," "Bad News Bears" and "Goonies," even more.

"Fun Size" is in that tradition--at least in terms of naughty stuff that tweens and teens will snicker over.

Pity it isn't as much fun as its title implies.

Victoria Justice jumps from Nickelodeon to the big screen with a PG-13 romp that only rarely romps, a movie that surrounds the lovely 19-year-old with funny people and struggles to find them laughs.

Justice (TV's "Victorious") plays Wren, a Cleveland high school senior dreaming of slipping off to New York and college.

First, she's got to talk mom (Chelsea Handler, given nothing funny) into letting her apply to NYU. Mom's distracted. Her grieving for her late husband has taken the form of dating a much younger, goofier, oddly named Keevin (Josh Pence).

And Mom is determined to hang out with Keevin's loser friends on Halloween, which ruins Wren's plans to hit the hot high school party that night with her hot-to-trot pal April (Jane Levy, amusingly on the money).

Wren has to babysit her 8-year-old brother, Albert (Jackson Nicoll), whose pranks are epic but who basically stopped talking when their dad died.

The romantic entanglement of the evening is Wren's desire to hook up with musician Aaron Riley (Thomas McDonell), who is throwing the party.

Meanwhile, her nerdy pal Roosevelt (Thomas Mann, of the raunchier teen farce "Project X") has little hope of making time with Wren, dressed as a tarty Dorothy from "The Wizard of Oz."

And nobody is making time with anybody, thanks to Albert's getaway. The plump ("Fun-size") kid escapes his sister's care and has many adventures involving pranks and run-ins with thugs, girls out clubbing and the like.

Even though we know where most of this is going, Max Werner's middling script is sprinkled with surprises--some rude, others downright crude. Houses are egged, a Volvo is "violated," fart jokes abound and Roosevelt's "moms" (Ana Gasteyer is one) score a couple of big laughs.

But Justice does nothing here that would make her stand out from the current crop of pretty young things trying to jump from TV to the movies.

"Fun Size" waddles along at half-speed, never building momentum. Even the good gags are robbed of their punch by the pedestrian way this thing was shot and cut.