Hollywood loves an inspirational teacher, and does more to promote the idea than a government ad campaign ever could. In the cinema, teachers are chalk-wielding, tweed-clad heroes who change lives, accompanied by a stirring soundtrack (Dead Poets Society (1989), Mona Lisa Smile (2003), Mr. Holland’s Opus (1995)). Every so often the record gets scratched to a more urban beat - witness Dangerous Minds (1995) - but our viewing pleasure is still shot to pieces by clichés: an education missionary has to prove that the pen is mightier than the gun in a classroom turned war zone. Half Nelson is different.

Dan Dunne (Ryan Gosling) is a teacher who smokes crack in the girls’ toilets. That’s the bald and bold premise of this American indie, from first-time filmmakers Anna Boden and Ryan Fleck. But what’s actually going on is a whole lot subtler. With a stylistic nod to social realism and ambient, dislocating music (by collective Broken Social Scene), Half Nelson uses an everyman profession to illuminate who we are, not just to give us a vision of the clichés we aspire to.

Dunne is a history teacher at a Brooklyn junior high, where he plays fast, loose and Hegelian with the curriculum – his favoured topics being civil rights and dialectics. He’s a base-head nihilist and a liberal idealist – his own dialectic of thesis and antithesis. We encounter Dunne as his life converges with that of 13 year-old pupil Drey (Shareeka Epps). Self-sufficient loners, both are on the verge of losing control. Drey’s brother is in prison for drug dealing, and her relationship with his friend Frank (Anthony Mackie) threatens to lead her the same way.

This small picture, with its deceptively plotless plot, is a great piece of filmmaking. Why? Because its makers deal with big ideas, and they understand their medium. Half Nelson is singularly cinematic in that it shows you more than it tells you – Fleck and Boden have faith in the eloquence of the image, in what is left unsaid rather than what is explicit. As such the script is beautifully sparse, shots echo each other and set up an understated tracery, the production design is downbeat and the acting makes you believe these characters have a life beyond the scenes we see. Gosling – Oscar-nominated for this role - imbues Dunne with an effortless cool and a pathetic destructiveness. While as Drey, Epps communicates a strength and gravitas way beyond her years, and magnetises the screen with a face that can be thundercloud or sunshine.

Refracted in the vignettes of Half Nelson is a disillusioned America: a young man employed by the government, who feels cut adrift by Iraq. What ever happened to the liberal dream? But this isn’t the film to rage at the dying of the light or to offer simple moral paradigms. Dunne may be a teacher, he may even be inspirational, but he’s also a soiled anti-hero, part Coupland part Dostoyevsky – sleazy, violent and alone. Dunne is in a hinterland, submerged in a haze of drugs and failed hope - caught in a headlock. Will he come up for air? As it turns full circle from opening shot to closing shot, this near-perfect film only gives us the mere hint of a synthesis, but perhaps it’s enough.