I never spent any time in a group home growing up and I don’t know anyone who did, so I have no way of knowing whether or not the stories told in Short Term 12 are realistic or overwrought. By some accounts, it’s realistic; by others, not so much. But for what it’s worth, I felt as if these were real stories about real people. Much of the credit of that has to go to breakout director/screenwriter Destin Cretton for pitching the vignettes just right, allowing stories to unfold naturally without shoving melodrama and plotting in your face. But the bedrock of this movie is in the performances, particularly that of Brie Larson. Somehow, Cretton and his crew found teenage actors that don’t overact; for all we know as the audience, we’re watching real group-home adolescents. John Gallagher Jr. also makes an impression, as the goofy, grounded boyfriend to Grace. But Brie Larson is the revelation. Without her wonderfully lived-in performance, Short Term 12 wouldn’t be the moving, great picture it is.