Half Nelson (15)

Whenever a film comes along about an inspirational teacher in a tough inner-city school, my immediate instinct is to bunk off for the day. We've already had 2007's heir to The Blackboard Jungle - Hilary Swank in Freedom Writers - and thus our quota of pious pedagogy has been filled for another year. When actor du jour Ryan Gosling was wildly praised and Oscar-nominated for his role as the inspirational you-know-what in a tough you-know-where, my misgivings about Half Nelson were primed: more redemption amid the chalk-dust.

So it's a relief and a pleasure to report that, while it ticks a few of the standard boxes, the film is much more closely concerned with ambiguities and unanswered questions. There is not a spoonful of preachiness on offer here. It's as if the director Ryan Fleck and the co-writer Anna Boden, making their feature debut, took the very notion of "role model" and turned it on its head.

Gosling stars as Dan Dunne, an amiable, loose-limbed teacher at a rundown Brooklyn high school who specialises in history but also coaches the girls' basketball team. He seems a relaxed kind of fellow on the surface, and his classes respond to his unpatronising, ironic manner and the enthusiasm for learning that drives him on. His great subject is the American civil rights movement, a subject to which his mostly black students are naturally sympathetic.

Indeed, Dan would be every parent's ideal teacher were it not for the fact that he is, outside of school, a hopeless drug addict. He seems to be getting away with it until one evening, after a coaching session, he lights up his crack pipe in the girls' loo and collapses on the floor. In walks one of his pupils, Drey (Shareeka Epps), a quiet, solemn girl who picks him up and helps him to his car.

From this moment a bond is forged between them, though which of the two most urgently needs saving is questionable. Drey, a lonely kid looked after by her divorced working mother, has an older brother doing jail time, and the charismatic drug dealer Frank (Anthony Mackie) who put him there now wants to recruit her as a drug-runner.

With penetrating subtlety the film inquires into the nature of moral responsibility. On the one hand, Dan is committed to keeping Drey on the straight and narrow, but once she knows that he's a junkie it becomes hard for him to play a father-figure. When, in a moment of candour, she asks him: "What's it like when you smoke that stuff?" he literally has no answer for her. In the classroom he keeps hounding a kid who cheats in tests, yet he hardly seems to realise the hypocrisy of his own, infinitely more serious cheating.

How Dan got into this pathetic state ("half nelson" is a wrestling hold that's difficult to escape) is not straightforwardly explained, but we pick up hints of unhappiness. His ex-girlfriend, herself a recovering addict, is about to be married. A dinner with his family seems to be a convivial occasion, but then his nice hippie parents are revealed to be frowzy old boozers: perhaps something has soured in them, too.

What's never actually mentioned, but surely underlies a great deal, is money. We presume from Dan's apartment that his job is poorly paid: can we presume further that the pressure of work and its paltry financial reward have pushed him into the false refuge of drugs? (But then, many people are viciously underpaid and still get by without a crack pipe).

The nature of dependency itself is harshly described, though its effects upon Dan's life as a whole are confusing. For much of the time he hardly seems able to stay awake, and as the movie goes on his behaviour veers from the erratic towards the dangerous: his wee-hours visit to a staff colleague whom he's been romancing goes right off the deep end. That he can hold down a full-time job is made to seem quite plausible, though I did wonder how a man with a drug habit like Dan's could work out and go running on so little food.

What never flags is the absolute conviction Gosling invests in the role. The details are good, his chewing-gum habit, loose tie and slouching walk quietly underlining that he's barely more grown-up than his students; but there's also a shambling blankness that Gosling nails superbly, a blankness where his self-esteem, perhaps, should be. "The kids keep me focused," he says, before tailing off in the maddeningly non-focused way he has. Best of all is the restraint in this provocative performance: whereas another actor, such as Edward Norton, would have indulged in a little grandstanding, Gosling never overdoes it. He is spare, discreet, unflamboyant - and truthful.

Almost as impressive is Shareeka Epps as Drey, a touching study in self-containment (and self-concealment) that bespeaks a maturity way beyond her years. Her body language can turn silence into a little drama of its own.

If the film were only the sum of these two performances it would be required viewing. As it is, the lean, insinuating screenplay by Fleck and Boden has a pace and punch that rank it among the very best of the independents from recent years. These writers seem to know exactly when to vary the mood and tempo, to cut from scene to scene, and to acknowledge the point at which argument fails and honesty has to take over. The best line is spoken by Dan to the drug dealer as each tries to claim ownership of Drey's best interests. It is simply this - "I don't know" - and it's the best because it echoes the provisional, unresolved tenor of the whole film.