Class struggle

Dan Dunne (Ryan Gosling) is the high school teacher you always wish you'd had. He's young, smart, cool, and committed, rebellious enough to go off the curriculum and enough of a natural showman to reel his students in with ideas that flatter their own minds. No one pays attention to these kids in a run-down school in Red Hook, Brooklyn, but Mr. Dunne does. He knows their secret: They want to learn.

They don't know his secret, though -- that he goes home every night and zonks himself into a coma with booze and crack. It isn't until Dan is busted by one of his pupils, a tough, lollipop-sucking girl named Drey (Shareeka Epps), that the two jagged halves of his life come together. They don't fit.

Gritty and terrifically human, ``Half Nelson" is not your big brother's Hollywood high school movie. There are no principals striding the hallways with baseball bats, no blond Malibu starlets teaching the inner-city kids how to read, no pat answers. The high here may be education, but that's just not enough for Dan, who drowns his idealism in a different kind of high. In addition to being a heartbreaking personal drama, ``Half Nelson" is, surprisingly, a withering allegory of the failure of the American left to change the world. What can one man do, especially when self-medication is so near at hand?

The relationship between Dan and Drey forms the emotional core of the movie, and it's charged with uncertainty on all sides. She's 13 and at the crossroads: One path leads to all the great, unruly concepts Dan is introducing -- and to the world itself -- and the other toward active complicity in her drug-battered neighborhood. Her older brother (Collins Pennie) is a small-time dealer serving time; his former boss Frank (Anthony Mackie) has taken it upon himself to look after Drey. He slips her money that her prison guard mother (Karen Chilton) wordlessly acknowledges, and he offers the girl employment as a drug runner. She's not biting, not yet.

It's a mark of the sneaky thoughtfulness of the script by writer-directors Ryan Fleck and Anna Boden that Frank's the most articulate person here. He genuinely cares about Drey, and he's self-aware enough to know that what he does is wrong; his collection of racist black caricatures marks his ironic detachment from both his race and his community. Other people's weaknesses are not his problem, and when it comes to the girl's well-intentioned teacher, well, Frank knows a junkie when he sees one.

Dan, by contrast, is a raging ball of privileged self-destruction. What makes the performance so startling is that the character rarely erupts; instead, he implodes softly and dangerously over the course of the film. Gosling has been the Next Big Thing for a few films now, but here he finally earns our respect; I can't think of another actor who could convey the intelligence, compassion, sorrow, and self-loathing Gosling puts across in a single glance. Each of Dan's crooked half-smiles represents another battle lost.

Why is this man-child such a wreck? His bookshelf at home, groaning with heavyweight tomes about history and dialectics, offers clues, as do the relationships he botches with an ex-girlfriend (Tina Holmes) and a fellow teacher (Monique Gabriela Curnen). ``Half Nelson" literally brings it home, though, in its finest sequence, a dinner party hosted by Dan's ex-hippie parents (Jay O. Sanders and Deborah Rush).

The complacency and bourgeois racism flow as thick as the wine, and the standard cluelessness of parents is compounded by everything these two and their generation could have done and didn't. ``You stopped the war," Dan offers his mom in an effort to cheer her up. ``That's nice," she nods, and pours herself another glass. If ``Half Nelson" had more scenes this pointed, it might be perfect. It also might hurt too much to bear.

Gosling may be the soul of ``Half Nelson," but Epps is the film's heart. Like her costar, the actress holds herself in abeyance; Drey simply watches and waits for life to tell her which way to go, and when it dawns on her that the decision is hers alone, we don't see it in her face but in her actions. The movie is too alert to provide easy redemption, but it allows for the possibility of connection and, in the end, says that's all we have to go on. Dan Dunne may be his own worst enemy, but he's the teacher and the lesson Drey has been needing her entire life.

Ty Burr can be reached at tburr@globe.com.