In the midst of Chile's Marxist government under President Salvador Allende, Father McEnroe introduces a program at the prestigious St. Patrick's Catholic prep school, allowing underprivileged children to attend for free. Among these students is Pedro Machuca, a boy from a poor background who becomes friends with Gonzalo Infante, a student from a liberal-bourgeois family. As they bond, Gonzalo is adopted by Pedro's slum family and gang, but their friendship is eventually disrupted by the adults, including General Pinochet's coup that overthrows Allende and leads to the persecution of his supporters.