The new roller derby movie “Whip It” should be approached with the same caution as the event itself: Pay your entry fee with the understanding that what you are about to witness is not a completely professional endeavor.

The movie stars Ellen Page (“Juno”) as Bliss, a high school kid stifled in a small Texas town who discovers roller derby in bustling nearby Austin as a way to find a life more suitable to her own tastes.

Roller derby's contemporary circumstances — underground and quirky — suit the movie, fashioned, like roller derby teams and their colorful costumes and names, with a casual, offbeat personality. The difference is Drew Barrymore, in her directorial debut, bringing considerable connections and fame to an adaptation of a humble book by real roller derby girl Bliss Cavendar. The result is a nationally-released film that probably would have been a scrappy underdog on the festival circuit without Barrymore behind it.

To her credit, “Whip It” does not make roller derby out to be anything more than it is: a fringe, retro entertainment as much about camaraderie, campy humor and skimpy costumes as serious competition. As in the movie, some of the girls are out to win and some are just out for the parties afterward.

Due to her slight build and quickness, Bliss becomes the star of the Hurl Scouts, which also features a hard-hitting and hard-partying character played by Barrymore, who ignores the finer details of the sport to the dismay of coach Razor (a wryly funny Andrew Wilson).

The movie ultimately suffers from the same kind of slacker attitude, paying more attention to cameos and one-liners than its often hackneyed plot, which takes forever to get to a few points anyone who has seen a sports or coming-of-age movie will be able to predict.

“Whip It” has its share of witty and genuine moments as well, and Page is likeable. But if Barrymore continues to direct, it'd be nice if she took it as more than a lark. (PG-13) 111 min. HHIII