Very bad behaviour: "NEDs"

If there's a throughline in the three features directed by Peter Mullan to date, it would seem to concern an idea of bad behaviour. Mullan's 1998 debut Orphans was a mischievous, black comic primer on how not to spend the eve of a loved one's funeral; its 2002 follow-up The Magdalene Sisters, notionally more serious in its dramatisation of true-life Irish histories, charted a rebellion against the brutal regime of a laundry for so-called "fallen" women. Part of these films' own bad behaviour was their cheeky-to-defiant refusal to conform to generic expectations: they simply wouldn't settle into predictable patterns or rhythms.

The Magdalene Sisters owed more to exploitation cinema than to the Angela's Ashes notion of suffering, and now - with his latest film NEDs (Non-Educated Delinquents) - Mullan has arrived at a coming-of-age movie that combines social-realist methods with the rise-to-power plotting of the Little Caesar-like gangster film and, eventually, the iconography (not to mention electronic score) of the 1970s slasher pic. Not the least of Mullan's accomplishments as a filmmaker working within the British film industry is to have made a brace of period movies that never once lapse into nostalgic conservatism - because they intuit the violence and bleakness of their times, and refuse to jolly it up for wider consumption.

In NEDs, for example, a parka-clad figure accosts youngsters outside the gates of their primary school, threatening to "kick [their] cunt[s] in"; a football boot full of firecrackers is volleyed through a window in a nice part of town; an alcoholic father stands in a hallway screaming for his "fat bitch" wife to come downstairs, so he can beat her; and a couple of ne'er-do-wells confront passers-by with a crossbow pointed through the car window. (They're listening to "This Town Ain't Big Enough For The Both Of Us". Of course they are.) The worst thing is that you don't see any of this coming - and, as a young man growing up in 1970s Glasgow, you're simply meant to take it all in your stride. It is, apparently, what puts hairs on your chest.

Mullan's protagonist John McGill (the extraordinary Conor McCarron) is a teenager living with both an aura of protection and a target on his back, the result of the mythical status afforded to an older brother expelled from school one year earlier for assaulting two teachers. What makes McGill a truly interesting figure is that - like Alex in A Clockwork Orange (not explicitly cited here, although Mullan's decision to score one extra-curricular knifefight to "(Dancin') Cheek to Cheek" suggests he may well have drawn lessons of his own from Kubrick) - the character is no mere thug or follower, but someone smart enough to understand the power of violence as both spectacle and statement: a young man who grasps precisely what each blow says and shows.

A bright kid, John finds his intelligence leaves him as much of an outsider as the knuckle-draggers and drongos lagging toward the back of the class. First to make a point, and eventually to prove himself the king of this particular jungle, this once-meek student, possessed of the cherubic face of a Tory backbencher, begins goading those around him: his classmates, students from rival schools and gangs, even the more peaceable members of staff. For Mullan, John McGill is wholly a product of his environment, and the film marks a return to the Magdalene theme of institutions, and the violence of institutions, portrayed as largely interchangeable from one another.

From his very first day of secondary school - arriving in his alloted classroom to see a boy having his hands viciously lashed for the crime of pushing in - McGill is plotting his escape: "If I work hard, I'll be out of here by Christmas," he boldly announces to his teacher later that morning. It's clear these boys have as much to fear from their supervisors as they do from one another outside the school gates - as the Magdalene Sisters did from the nuns before them. John's form tutor can be overheard bemoaning his own Catholic education at one point: the sense is that these teachers are doing unto others what was done unto themselves. In other words, the cycle continues: with no escape from its brutalities, the only choice is to pick your gang and knuckle down.

For its first half, dealing with this least sentimental of educations, NEDs plays as as much a prison movie as A Prophet, only here the scenes of day release - boys mooching around municipal playgrounds, or chasing rival gangs through parks - make greater sense. After Billy Elliot, Velvet Goldmine and Control, Mullan comes late to the idea everyone in the 70s spent some time listening to Bolan in their bedrooms; more convincing is his low-key evocation of the school disco - Wizzard and The Sweet presiding over a scene of gently grim awkwardness - where the boys, at all points looking over their dance partners' shoulders, appear more concerned with impressing one another, being seen to be "a man", than the girls they're with.

Mullan has a real eye for such details and faces: the headmaster who, striding across the playground, has to remove a cigarette in order to blow his whistle; the Latin master who accuses his class of being "in holiday mode"; the noisy, stolen first kisses in mossy graveyards. Narratively, the film is more jolting. McGill's descent into attempted murder comes over as especially swift, if typical of the rashness and breakneck development Mullan is surely getting at. (Perhaps you had to grow up quickly back then.) And the intervention of a very Scottish Christ the Redeemer (to the sounds of the New Seekers, no less) really does come out of nowhere - though it's arguably the Godly smackdown or wake-up call our boy needs at that moment.

At two hours, NEDs certainly sprawls, and it doesn't quite manage the sustained power and horror The Magdalene Sisters generated. A coda in a safari park, though funny and thematically resonant, feels like an attempt to get us past the single most disturbing image in the film: nothing bloody, this time, but two men very much cheek-to-cheek in an embrace of something not necessarily positive. Yet its underlying structures throughout are clear in such things as the cursory presence of John's older brother, the way the schoolteachers seem as much prisoners of the system as their charges, and in the father (Mullan himself, gaunt and terse and so much scarier for being clad in his Sunday best throughout) who only ever stumbles into his son's life to rescue a bottle-opener from a desk drawer. Its grit and salt feel like vital correctives to our prevailing culture of pretty-pristine Upstairs Downstairs and Downton Abbeys - a reminder of what we have had to put behind us, or grow out of - and in somehow finding new and specific things to growl about men and violence, it has to count as a raggedy sort of triumph.

NEDs opens in cinemas nationwide from Friday.