Somehow I missed Half Nelson at both Sundance and in critics’ screenings. It’s not an easy picture, neither in terms of subject — an otherwise over-earnest Brooklyn junior high school teacher (Ryan Gosling) buys crack from the same neighborhood element threatening his students’ welfare — nor execution, which loops around the characters’ intentions and actions like a never-swept spiral staircase. But it’s worthy, in no small part because of Gosling’s strong, understated performance and the incredible generosity of his pubescent costar, Shareeka Epps, who plays the student who’s onto his coke problem partly because she’s already submerged in the perils of that world.

That Epps has already developed her chops enough to bestow generosity upon her fellow actors speaks volumes about her tremendous talent; she resorts to none of the tricks most young actors pass off as acting: no flat, unmitigated stare; no mugging. She watches instead, with eyebrows that punctuate a whole scene singlehandedly and a big grin that you wish her character had opportunity to flash more. But as Dre, the daughter of a single MTA worker (Karen Chilton) rueful about her daughter’s isolation but too mired in scraping together her bare necessities to otherwise nurture her, Epps is more of a badass who terrorizes the biggest thug in the schoolyard yet still weeps over her brother in prison, and over her teacher’s terrible folly. She is intact, in other words, which partly stems from bright lights like her smart teacher who ignores the prescribed school curriculum to teach his students critical thought — to think beyond the black-and-whites literally and figuratively prescribed by their neighborhood, their media. Their whole world, in other words.

Here’s where the film falls out, for though moralizing would do no good in a film invested on every level in the greys of life, it’s a bitter pill to swallow that the predicament of the student preyed upon by drug dealer is equal to that of the teacher buying from that dealer. It’s hard to forgive those particular trespasses in an adult entrusted with the education of teens who receive very little other support — and though we eventually sit through an evening with his boozy, liberal (with all the true-lefties’ attendant negative associations to that term) family that sheds light on his strain of inner turbulence, it ain’t hardly enough.

It’s an explanation, though, if not an excuse, and that’s all that this small, quiet triumph seeks to offer. To its credit. I’m grateful I finally did surrender to its sleepy, sad stupor.