Plucky kids from hardscrabble 'hood make good: a well-worn story line, but one that works, again, in "Brooklyn Castle."

This documentary, which won an Audience Award at SXSW, follows the unlikely chess champions of an inner-city middle school where most of the students live below the poverty line.

Thanks to a caring teacher, a supportive coach and an enthusiastic principal, the chess program is a very cool place to be, and a possible ticket to college scholarships. Chess is also an antidote to distraction in an A.D.D. world; the kids must give their brains a workout and concentrate for long periods, which in turn helps them with their studies.

Director Katie Dellamaggiore manages to build suspense, no easy feat when your visual is a bunch of silent chess players hunched over boards in hotel meeting rooms. She gradually reveals the personalities and backgrounds of Pobo, Rochelle, Justus, Alexis and Patrick, whose moods range from anxious to cocky to heartbroken as they work their way up and down the rankings, and write passionate letters to politicians when the program's funding is threatened. By the time their hard work culminates in a trip to Minneapolis for the 2010 nationals, it's impossible not to root for all of them equally.

Like "Spellbound," the spelling-bee documentary, this doc is an ode to the triumph and despair of competitions made more poignant by the tender age of the contestants. It's also an effective PSA for why funding extracurricular school programs is so crucial: They can mean more to children's lifelong success than learning their ABCs does.

Dellamaggiore clearly adores her subjects -- maybe a bit too much -- but so what? You will, too. (Rating: PG.)