Maggie Gyllenhaal is most comfortable playing complicated, flawed women, whether in her break-out role in the dark sex comedy "Secretary" or even reprising the part of Rachel Dawes in "The Dark Knight." So when she was asked to play the determined single mother willing to take on the public school bureaucracy in "Won't Back Down," she was up for it only if she could make the character human and relatable.

"I didn't want to tell the story of someone who does something heroic, who is immediately identifiable as an exceptional, remarkable, heroic person when she starts," said Gyllenhaal, who turns the role of single mother Jamie Fitzpatrick into a harried, disorganized woman who often has time only to feed her daughter pop tarts for breakfast before rushing her off to school. "I wanted many people to be able to relate to the possibility of doing something heroic. I also wanted her to be really flawed as a mother, and by that I mean like any other mother, trying to manage as best she can, making mistakes, sometimes being able to think about them and sometimes not."

Playing such a character required a lot of conversations with Daniel Barnz, the co-writer and director, throughout the film's 10-week shoot in Pittsburgh.

"It's funny how everyone gets concerned when you are playing a heroine in a big movie that you be really relatable and likable," said Gyllenhaal, who is just returning to work after her second maternity leave. "All the way through, it was a fine line to walk."

Gyllenhaal stars opposite Viola Davis, who plays a beleaguered teacher at the same elementary school that Gyllenhaal's character's daughter attends. Together, the two women must go up against a resistant faculty, a resigned group of parents and an entrenched school board to take over the failing institution. Though the film isn't based on any one true story, poor-performing schools around the country are experiencing similar public advocacy.

Set to bow on Sept. 28, "Won't Back Down" is reminiscent of such populist, issue-driven films as the Julia Roberts-starrer "Erin Brockovich" and the 1979 Oscar winner "Norma Rae." Gyllenhaal recognizes that although the issues on this one are different, the same challenges remain: "In this movie, you had to find the emotional life within the politics."