Now and then, a kid makes a run for it. In Short Term 12, Destin Daniel Cretton's low-key, high-emotion indie about a foster-care facility for at-risk teens, there are periodic efforts to escape. A breakout, a crazed tear across the scruffy lawn, and once they're beyond the gate, they can't be touched. Gone.

A pair of attempted getaways bookend Short Term 12, but it's what happens in between that really matters. This is a film about hurt and healing, isolation and fear, need and rage - and it's not just the motley, messed-up crew of 14- and 15-year-olds who are trying to cope, trying to get better.

Grace, the facility supervisor, may seem like she's got it all together - a cool, twentysomething caregiver who acts more like an older sister to these adolescents than an authority figure. But she has her issues. They run silent and deep.

Brie Larson gives a career-defining performance as Grace; the actress has this woman down, from the beat-up bike she rides to and from work to the beat-up look in her eyes, which she hides with an outsized empathy. Grace lives with, and works with, Mason (a very good John Gallagher Jr.), who is rightly in awe of his partner's strength, her priorities, her instincts, her goofy humor.

When a new staffer, Nate (Rami Malek), shows up for his first week on the job, we get to see the facility, how it operates, and who its residents are - and the challenges its young team of overseers faces. There is good reason there are no scissors, razors, belts allowed.

In lesser hands, Short Term 12 could have been the stuff of an afterschool special, a Lifetime TV melodrama, with its walking-case studies of drug addiction, sexual abuse, violence, eating disorders, and self-mutilation. But the kids Cretton has cast display few signs of effort, of overdoing it.

Alex Calloway's Sammy - a skinny teen lost in his fantasy world of dolls and plush toys - feels terribly right. Keith Stanfield is brooding and intense as Marcus, about to be released from care because he is turning 18. And Kaitlyn Dever as Jaden, a new intake with special privileges, bristles with loathing - and self-loathing.

Grace's efforts to connect with Jaden become pivotal to the narrative, revealing as much about her own history as it does about her scowling, goth-girl charge.

Short Term 12 is full of telling detail (the pencil smudges on Grace's wrist, from her drawing sessions with Mason - perfect!) and full of compassion for its characters. It has heart, and heartbreak. And because it is so committed to getting these things, and these people, right, the movie leaves you feeling not depressed or despairing, but inspired. That's not a bad trick.

Short Term 12 ***1/2 (Out of 4 stars)

Directed by Destin Cretton. With Brie Larson, Frantz Turner, John Gallagher Jr., and Kaitlyn Dever. Distributed by Cinedigm.

Running time: 1 hour, 36 mins.

Parent's guide: R (sex, profanity, drugs, adult themes)

Playing at: Ritz Five EndText

Contact Steven Rea at 215-854-5629, srea@phillynews.com, or follow on Twitter @Steven_Rea. Read his blog, "On Movies Online," at www.inquirer.com/onmovies