WHEN WE FIRST meet 15-year-old Liam (Martin Compston), he's peering heavenward at the stars through a telescope, dreaming of a better life beyond the confines of the Glasgow tenements. Considering his mother is in jail, mom's boyfriend is slightly south of scum, and his dim-witted best friend, Pinball (William Ruane), ricochets from one mindless stimulation to the next, like his namesake, it would make sense that Liam's idea of Eden might be a simple trailer by the sea for him and his soon-to-be-released mum. And what's the best way to make some quick cash in lower-income neighborhoods? How about selling drugs and striking a Faustian bargain with the local crime czar? By the time we leave our come-of-age hero on his 16th birthday, he's staring into the dead end of a filthy, boggy marsh, contemplating a future that's decidedly bleaker than his wayward adolescence. Long the cinematic voice of the British left, filmmaker-muckraker Ken Loach (Kes) forgoes the Marxist-mouthpiece caricatures of recent efforts in favor of the familiar ground of working-class melodrama marinated in realism. Don't think the activist director lost interest in underground politics or underdog struggles, however; by setting this tale of a gangster in training in an environment in which even a stroller-pushing mother knows where the local drug den is, Loach speaks his social commentary loud and clear even without the polemic speeches. He's immensely helped by Compston, an actor who turns the morally ambiguous Liam into a combination of Antoine Doinel and the classic Anglo angry young man. Thanks to him, it's hard not to feel for Liam even as he digs his self-destructive ditch deeper downward to get up in the world, a paradox of the class system that Sweet Sixteen may sentimentalize in its narrative but wisely offers no easy answers to. (David Fear)