There have been many films about children coming of age in a political cauldron. Louis Malle's ''Lacombe Lucien" (1974) and ''Au Revoir, Les Enfants" (1987), for instance, are two of the great ones. Andres Wood's ''Machuca" is one of the good ones, with an unerring eye for time and place that's counterbalanced by an overly passive, if sympathetic, central character. The movie's clearly made from the raw material of the Chilean filmmaker's own childhood experiences during the early-'70s presidency of Salvador Allende and the right-wing coup that toppled him, and that subjectivity benefits ''Machuca" while keeping it from fully attaining flight.
It's a tale powerfully told, nevertheless, with an unusual vantage point in its upper-class young hero. Thirteen-year-old Gonzalo (Matias Quer) is one of the lucky ones: He attends a private English-language school, lives in a posh Santiago apartment, and his father (Francisco Reyes) can pay for black-market groceries while the poor and middle class wait in long lines. His spoiled sister (Gabriela Medina) is dating a rightist thug (Tiago Correa), and his fashion-plate mother (Aline Kuppenheim) is carrying on an open affair with an aging industrialist (Federico Luppi) who makes no secret of his hatred for Allende's socialist aims. Gonzalo takes this all in and says nothing, beyond the occasional muttered insult toward his mother.
Chile's underclass, by contrast, is behind Allende all the way, and Gonzalo's life changes when the school's leftist priest, Father McEnroe (Ernesto Malbran), opens his classroom to a number of poor neighborhood children, dark mestizo kids with holes in their sweaters. Most of the rich kids taunt the newcomers, but Gonzalo, already a quiet outcast, befriends the pint-sized Pedro Machuca (Ariel Mateluna). The two spend after-school hours crisscrossing Chile's rigid social barriers: Gonzalo bicycles down to the shantytown where Pedro lives, while Pedro spends a night at Gonzalo's house, marveling at the opulence. It can't last, and it doesn't.
''Machuca" sketches in the details of dress and caste and social ferment with remarkable skill, and it isn't particularly subtle about whom it likes and dislikes. Gonzalo's parents are upper-class twits, and their friends are worse, arrogant and panicked by what they see as the mob at the door. Pedro's life is drawn with more nuance; his father (Alejandro Trejo), a bitter alcoholic wreck, briefly shows up to warn his son away from Gonzalo, and his words have the sting of truth: ''In five years, he'll be in college and you'll be cleaning toilets."
Gonzalo's cousin Silvana (Manuela Martelli) offers Gonzalo hardheaded cynicism -- he joins her and Pedro in selling Chilean flags to both left-wing and right-wing marchers -- and stirs his nascent hormones: A playful and suddenly erotic scene with the three teenagers and a can of condensed milk is the most powerful moment in the movie.
Until the other shoe drops, that is, and Allende is overthrown on Sept. 11, 1973 -- a date that has as much resonance for Chileans as 9/11/01 has for Americans. Gonzalo watches the bloody events on TV and then in the streets, where he is at last required to take sides. It's a heart-wrenching scene, and one that prompts the viewer to search his or her own heart for answers that don't come easily.
The final moments of the film are both terribly moving and strangely muted. As Quer plays him, Gonzalo is not so much a character as a placid observer, a receptor through which Wood can come to grips with his country's past and his own feelings of guilt. This is the trap presented by all memory tales, and the filmmaker hasn't found his way out of it. ''Machuca" is an important act of bearing witness, but there's a hollow spot at its core where there needs to be a human being.
Ty Burr can be reached at email@example.com.