It's a matter of conjecture whether revered comedian WC Fields told his peers to never work with animals or children.

Regardless of the provenance, British director Stephen Daldry has ignored the sage advice and taken on projects that demand powerhouse performances from inexperienced performers.

In 2000, he worked closely with newcomer Jamie Bell on Billy Elliot, guiding his young star to a BAFTA as Best Actor.

A decade later, he performed similar miracles in Extremely Loud & Incredibly Close, wringing tears from 12-year-old Thomas Horn as a socially awkward boy haunted by the death of his father in the September 11 attacks.

Daldry's talent for identifying and skilfully nurturing raw talent is in evidence again in Trash.

Based on Andy Mulligan's novel, which has been adapted for the screen by Richard Curtis, this rousing tale of courage in the favelas of Rio de Janeiro is blessed with luminous performances from non-professionals Rickson Tevez, Eduardo Luiz and Gabriel Weinstein.

Combining the gritty setting of City Of God with the life-affirming cheer of Slumdog Millionaire, Daldry's film is an undeniable crowd-pleaser.

While the plot ultimately falls apart in the final act, the teenage protagonists light up every frame.

Shortly before he is arrested and tortured, Jose Angelo (Wagner Moura) flings a wallet into a passing garbage truck, which is destined for the local tip.

Among the throng of children scavenging the tip for plastics is Raphael (Rickson Tevez), who finds the wallet and secretly shares the contents with best friend Gardo (Eduardo Luiz).

When cops led by police inspector Frederico (Selton Mello) descend on the site, promising a handsome reward for the wallet, the boys realise the precariousness of their situation.

They seek out pint-sized outcast Rato (Gabriel Weinstein), who lives in the sewers, and he leads a merry dance to a locker in the city centre, which is the first clue to a conspiracy involving mayoral hopeful Antonio Santos (Stepan Nercessian).

Unable to trust the authorities, the boys turn to Father Juilliard (Martin Sheen), who runs the local ministry and his plucky assistant Olivia (Rooney Mara) but they are no match for Federico and his thuggish men.

Trash is anything but emotionally manipulative rubbish but Daldry's film does fall short of the emotional wallop promised in heart-breaking opening scenes.

Tevez, Luiz and Weinstein are naturals in front of the camera, sharing palpable screen chemistry that compels us to root for the boys against Mello's sadistic cop.

Rooney is underused while Sheen lends a warm, avuncular glow to his alcohol-swilling man of the cloth, who advises Olivia to keep her nose out of the boy's affairs.

"Don't waste your life fighting battles that make you bitter or make you dead," he sermonises.

It would be a dull denouement if she listened.