The fat, lazy public school teacher who can't be bothered to stop diddling with her phone or shopping for shoes online while her second-grade class erupts into mayhem in the opening scene of Won't Back Down isn't the most despicable entity in this tearjerker. That would be the union that protects her, the same malevolent force in Davis Guggenheim's horribly argued pro-charter-school documentary from 2010, Waiting for Superman (both films were funded by Walden Media, led by a conservative billionaire). Inspired by "parent-trigger laws," which allow parents to take over failing public schools and are now permitted in a handful of states--though not the one this film is set in--Won't Back Down tracks the invincible collaboration between Pittsburghers Jamie (Maggie Gyllenhaal), a single mother working two jobs whose dyslexic daughter is only falling further behind at F-ranked Adams Elementary, and Nona (Viola Davis), a teacher at Adams fed up with the administration's apathy and fretting over her own learning-disabled kid. Viewed solely as maternal melodrama, Won't Back Down succeeds; its actresses rouse, rage, and rue admirably (though in Davis's case, marveling at yet another fine performance doesn't stop you from wishing that her first leading role was in a worthier vehicle). But there's no prettying up the movie's vilifying of teachers' unions--an easy enough scapegoat for the larger, more intractable economic problems also ignored in Guggenheim's film and by most politicians of any stripe.