Drew Barrymore has devoted more time than most people to growing up and has done it more publicly than most people, too. At age 34, she has been acting for nearly three decades. Here she makes her directing debut with a coming of age story that may be conventional in structure but has some unexpected warmth and wisdom.

Ellen Page of “Juno” plays Bliss, a small-town girl whose undefined sense of displacement and dissatisfaction never got more specific than feeling inauthentic in the beauty pageants her mother insists on or working as a waitress at a barbecue place called the Oink Joint. She feels fully herself only with her best friend Pash (the bountifully freckled Alia Shawkat), until she gets a flier for a roller derby. She convinces Pash to go with her. The roller derby girls are full-on smash and bash and brash and completely unabashed in a way that makes Bliss feel fully alive. Even though her “last pair of roller skates had Barbies on them” and she is tiny and not especially athletic — not to mention that her parents would never approve — she decides to try out.

Even in movieland, girl squab Ellen Page seems like someone you skate over. But they do the Harry Potter thing and give her the one attribute that makes it possible for her to compete with women three times her size and five times her weight class. She is very fast. And that is how she is taken on by the “Hurl Scouts,” including Maggie Mayhem (Saturday Night Live’s Kristin Wiig), Bloody Holly (stuntwoman Zoe Bell), Rosa Sparks (rapper Eve), and Smashley Simpson (director Barrymore). Their Girl Scout-inspired uniforms and cheerfully bad attitude make her feel at home. Bliss becomes Babe Ruthless and she is on the team. And before long, she has a fan, a handsome young musician (Landon Pigg), who likes her very much.

Do you think that Bliss is about to embark on a journey far more fraught with peril than the roller rink? Well, then, you’ve seen a movie before. Yes, there will be complications and painful disappointments involving her friend, her parents, the musician, and the friend.

What is best about this is the way Barrymore gently sells the niceness of it all. It turns out that roller girls just wanna have fun and that the sisterhood of the traveling skates is one big happy family. Barrymore has spoken frankly of her essentially parent-less childhood and here, as she often does in movies, she conveys a young girl’s feelings of isolation and the longing for motherly guidance. Bliss finds that guidance from an unexpected place in one of the movie’s most affecting scenes. The overt message about girl empowerment may focus on hip checks and punches, but what lingers are the lessons that nothing is more powerful than forgiveness, that loyalty to others enhances your ability to define your own space, and that at every level within and outside the film sistas are doing it for themselves.