FOR WRITER/director Daniel Barnz ("Beastly"), the public-school empowerment drama "Won't Back Down," starring Maggie Gyllenhaal and Viola Davis and opening Friday, is something of a passion project.

"I'm the son of two teachers," he said at the Loews Hotel at 12th and Market, the morning after a screening for the film attended by Mayor Nutter and education experts.

"My grandmother was a teacher. My sister-in-law teaches in the public-school system in New York, and my mother-in-law founded the first alternative middle school in New York City. She's still the principal."

So when "Won't Back Down" gets pegged as simply an antiunion movie, the affable Barnz, who grew up in Gladwyne, gets a little agitated.

"I think it's a shame people perceive this as an anti-union movie," he said.

"I'm a liberal Democrat, very pro-union, a member of two unions. I marched with my union a couple years ago when we were on strike. What I tried to do with the movie is celebrate all the things that unions do, while looking at some of the ways that the agenda of the teachers union may not always reflect the best interests of children."

In the film, Davis and Gyllenhaal play mothers who take a tough stance against bureaucracy to save their children's troubled inner-city school.

"My position is what Ving Rhames [as a school principal] says in the movie: 'You can support and criticize unions.' That's exactly how I feel about it," said Barnes, who also believes critics are overlooking what the movie says about how unions support teachers.

"Maggie's boyfriend's character - his entire story line is that this is a great teacher who was inspired by a teacher who was allowed to keep his job because of the teachers union."

He continued, "Honestly, when I made the movie, I knew this was a very divisive world and debate, but I made a movie about people coming together - and that's one of the central narratives - so I think there was a very optimistic part of me that hoped that people would embrace that aspect of it. But what has happened with some of the debate is that it has gotten off point and so people want to nitpick the accuracies of the movie. I researched the movie very carefully. Every aspect of the film is grounded in reality.

"What's distressing to me about the controversy is that people make this into a very adult-centric debate, and really, what the whole movie is about is how we can come together to make things better for kids.

"I think the movie really offers up a very hopeful message about how we can do that."

Barnz said "Won't Back Down" screened to wildly positive response at both political conventions. The screening last week in Philadelphia was an eye-opener, and not just because it was his first visit here in decades.

"My family moved away when I went to college," Barnz said, "so I haven't been back in 20 years. The city looks great, really beautiful."

And his Philadelphia moviegoing experience?

"In L.A. you tend to get more respectful audiences," he said. "This was a very vocal crowd, and they were laughing and gasping and cheering, and that's such a joy as a filmmaker to see those kinds of reactions. There was also a really animated discussion after."

Barnz hopes the controversy will eventually die down and people will see the film for what he meant it to be - and start working together to bring change to classrooms that aren't working.

"I've been able to see what great teachers can do," he said, "and a point of the film is to celebrate great teaching. The greatest compliments I've received from the movie are when people come up to me afterward and they say, 'Your movie made me want to go and be a teacher.' Or they say, 'I taught for 40 years - your movie made me want to go back into the classroom.' "