Brie Larson uses a Super Soaker to keep order at "Short Term 12."

Do not miss Short Term 12 when it plays at the Modern this weekend, for it has the best female lead performance I’ve seen all year. It comes from former pop singer Brie Larson. You probably saw this 24-year-old actress as the token girl in 21 Jump Street, though she has had more rewarding parts this year in The Spectacular Now and Don Jon. I first noticed her three years ago, when I saw her play an intimidating, robotically sexy rock singer in Scott Pilgrim vs. the World and then turn around and play a bitter gay stoner in Rampart a few months later. I had one of those, “whoa, that’s the same person?” moments when I saw her name in the credits.

So she has crazy range, but does she have depth? In Short Term 12 she plays Grace, the supervisor of a group home providing temporary shelter for children who have no one to care for them. You can see why Grace has been put in charge of the place, even though she’s so young. She’s a crisp and efficient administrator, quick to discipline the kids when they step out of line but just as quick to show kindness and caring toward them when they need it. She’s also possessed of a wry sense of humor and a talent for drawing. She seems too good to be true, but then two things happen that crack her open. First, she discovers she’s pregnant by her boyfriend Mason (John Gallagher Jr.), who is also one of her staffers at the home. Then, the home takes in an angry, self-mutilating 14-year-old girl named Jayden (Kaitlyn Dever). Grace turns out to be the sort of person who throws herself into other people’s problems as a way of ignoring her own, but Jayden’s case makes that impossible.

Writer-director Destin Daniel Cretton has a feel for the rhythms and atmosphere of the home, and you won’t be surprised to learn that he spent some years working in such a facility. (The film was shot in an actual former group home in San Francisco that had been defunded by the government.) I wish Mason weren’t so infinitely patient and kind, and I wish Jayden’s hidden trauma and Grace’s didn’t match up so neatly. I sniffed out said trauma rather early in this film, and the mere fact that the heroine is named Grace is a bit anvilicious in itself.

Texas Book of Beasts 300x250 JPG

If Larson weren’t so great, this movie would probably be just another hack indie drama. But she eventually reveals the outwardly cool and authoritative, in the way Grace slumps over when she learns her father is getting out of prison or the anger that comes boiling to the surface when a social worker sends Jayden back home. Larson is indelible as Mason begs Grace to tell him what’s eating at her and Grace just stands there, looking utterly helpless and afraid before she chokes out the words, “I can’t.” (Close to this is the reading that Dever gives to a fable that Jayden has written about an octopus and a shark. It’s terribly sad.) As Grace steels herself to break a whole lot of laws to get Jayden out of her situation, Larson shows us just how determined and compassionate and screwed-up she is. Unfortunately, this actress has little chance of getting an Oscar nomination because not enough people know who she is, but you can still see her performance for one weekend only at the Modern.

One last note that may interest only me: Larson apparently likes to relax by designing typefaces.