Slowly the children grasp what's required of them and oblige with growing excitement, a chorus of suggestions which creates a chip shop as you listen, from the babble of the wall-mounted telly to the frizzle of wet chips going into the fryer. It is a teacher's fantasy - the longed-for alchemy of education, all that dull base metal glinting into gold.
But the scene is not simply wishful thinking. "I taught those lessons, you see," says Jimmy McGovern, creator of Cracker. Indeed, McGovern taught the lessons twice - the first time round as a zealous young teacher himself and, more recently, as a television writer, researching his new series, Channel 4's Hearts and Minds, which follows the firework career of a young comprehensive teacher - soaring aspirations and swift burnout.
The intervening years have had a sobering effect. "I was constantly putting out fires," McGovern says of his return to the classroom. "In the past, I would have stood there at the front and controlled it somehow - knackered at the end of it - but I wouldhave controlled it. But when I went back, some kids would just lose concentration ... I got a lot more tired a lot quicker the second time. Everyone I spoke to said the same thing - since the Eighties there's been a terrible change."
These days McGovern describes himself as "a total reactionary" about education. In fact, his manifesto sounds liberal at first, but there is a sting in the tail. "If you're talking about the future of our children, then you take it seriously. You put money in, you give the teachers a massive pay rise, you clean up the environment in which they teach and then you put them all on short-term contracts and sack the ones that don't deliver."
Hearts and Minds, like all of McGovern's work, is a striking mixture of courtroom and confessional, a piece of dramatic cross-examination in which, more often than not, it's his own past that's in the dock. In Cracker, he drew on personal experience of compulsive gambling to fill out Robbie Coltrane's ample character; here McGovern returns to what came next.
"I trained quite late in life after a background of menial jobs. One of the great attractions was that I could get a mature student's grant, which, with a wife and three kids, was a good screw, and I could work in the holidays tax-free ... I went back intofurther education in my late twenties and it just transformed me. I was gambling at the time and it stopped me."
By his own account he entered teaching as if it were a rescue mission, determined to redress the perceived injustices of his own education - that of a bright but disadvantaged boy in a Jesuit school with social aspirations.
"I thought I understood poverty," he says. "I thought if anybody can understand what a black kid from the inner city is going through it would be me."
In Hearts and Minds, Drew McKenzie (played by Christopher Eccleston, DCI Bilborough in Cracker) puts the passion into words: "Education changed my life, know what I mean? And I want to see it change a lot more lives."
That passion is soon dulled by the pettiness of his colleagues and the abrasive struggle for children's attention, again drawn from McGovern's experience.
"The main thing was a lousy timetable, where the head of department gets all the cream, so you haven't got the respite of an academic class. But it was also the small-minded attitudes of people in the staffroom. These two guys, for instance, would talk about Coronation Street all the time. I thought it was a double act and it took me a year to realise they were serious."
His own escape came by way of Brookside, which he joined shortly after its launch and for which he wrote more than 80 episodes. There was a lean period after he left the soap and before Cracker transformed him from an industry secret into a household name, but the idea of a school drama has been around for years. The series was commissioned and begun before Cracker's great success.
"Years ago I argued that the only way to do a Hill Street Blues in this country is in a school. It's the only thing you can think of that has that element of business, of people crossing and snatched conversations."
He's certainly achieved this. At times, the soundtrack of Hearts and Mind is as densely layered as an Altman film; you are plunged in at the deep end along with Drew. But the history of the project hasn't been particularly easy, partly because the landscape McGovern was trying to describe was changing by the week. The issue of opting out didn't even exist in the early episodes and there were other drafts in which they loomed far larger than they do now.
There have been other changes, too. "The first two episodes were binned by Peter Ansorge [head of drama at Channel 4]," says McGovern. "At the time, I was cursing him but he was right, because they were set in a teacher training college and now it has focus."
It has many other things besides, in particular a sharp eye for the glancing details of school life, whether comic (a small boy who has superglued a cola can to his lip and his waiting disconsolately outside the head's study) or depressing (the petty malice of the staffroom).
McGovern admits, without conspicuous regret, that he was no more of a staffroom diplomat than Drew is, but if he is rewriting the history of old wars, he does it with an unusual honesty and even-handedness. Hearts and Minds may be an arraignment of the system, of its cynicism and indifference, but it isn't sentimental about naive young crusaders or simple-minded in its politics.
In one fine scene, Drew is discovered by a more experienced colleague in the middle of a full-blown classroom riot. "What's going on?" she shouts above the din. "Improvised drama - conflict," he explains plaintively. "I was trying to get them to understand Northern Ireland." More darkly still, his well-meaning attempts to bring a young Muslim girl out of her cultural isolation come close to classroom bullying.
And while McGovern himself voted against opting out when the issue arose at his son's school, his portrait of a headmaster who wants to do just that in Hearts and Minds is sympathetic and open-minded about the desire to manage the unmanageable. It is theopponents of opting-out who play dirty.
This isn't surprising: despite its passion for social underdogs, McGovern's writing has never been deferential to the conventional boundaries of liberal opinion - a quality that got him into trouble with Cracker and almost certainly will do again. One ofthe villains in Hearts and Minds, for example, is a black teacher who boasts that he's unsackable and spends his time playing cards with his more unruly pupils. A less mischievous writer, one less determined to improvise conflict for the sake of understanding, might have decided he had quite enough on his hands already.
`Hearts and Minds' starts its four-week run next Thursday, 16 February, at 10pm on Channel 4.
It's not like that in our school, Jimmy: Finally, it's here, the school we all wanted to teach in, the classrooms we all loved to play in, and the teachers we all loved to play up on.
For this is a story of drunkenness, debauchery, rioting and intrigue - and that's just the staffroom. The pupils, meanwhile, are simply unkempt, obstructive and disaffected while their parents are, by turns, threatening and ignorant, providing the hapless role models that perpetuate the inevitable cycle of deprivation.
It all happens at Northfield grant-maintained school, set to rise from the ashes of the former council comprehensive, the noticeboard of which is being incinerated as the series begins.
Jimmy McGovern has brought his own experiences of learning and teaching to a desperate school set in a derelict community. Only one set of textbooks is available for several classes, and there is a single video-recorder for pupils who are invariably hostile to discipline and learning, and often with the active support of their teachers.
Little wonder, then, that the young, idealistic Drew McKenzie supports the headmaster's espousing of the grant-maintained cause. Not only that, but it is a condition of his employment as a "probationer".
A Maguire, the headmaster, is the inspiration behind the move towards opting out, and a cross between David Owen and Machiavelli. He succeeds not only in putting his own particular stamp upon the new, upmarket noticeboard but also upon the philosophy of the new-fashioned school by rejecting "unsuitable" local children who show any tendencies that might require the services of an educational psychologist. "Like having a nit-nurse," he tells Drew.
Is it true? Could it happen in your local comprehensive? Well, there remain idealistic teachers such as Drew, and their work does seriously intrude into their families' lives'; there are teachers who are gay and who, faced with hostility from both pupilsand colleagues, turn to the bottle for comfort; there must be black teachers who instruct their charges in baffling police procedures; and, I dare say, some headteachers who are frustrated company directors.
Certain inaccuracies and anomalies intrude without necessarily being intrusive: "probationers" have long since gone to be replaced by NQTs (newly qualified teachers); sets of Walkabout have been replaced by books written since Jimmy was a teacher, although, of course, Julius Caesar and his ilk have returned with an academic vengeance; and league tables emphasising inherent ability have had their effect upon some schools' recruitment policies.
Unlike Northfield School, whether in grant-maintained or council form, few schools have 12 pupils per class and only 12 teachers with which to populate the staffroom. Whether this was to do with tokenism or tight Channel 4 budgets is unclear.
Moreover, there now exists considerable evidence to show that most grant-maintained schools have been able to demonstrate that children are the absolute priority.
Our own school, situated in a strangely similar area to that of Northfield, has employed two additional "one-to-one" special needs teachers, a school nurse (who is perfectly able to act as nit-nurse should the occasion demand), and has been able to introduce our children to the hitherto undiscovered delights of textbooks.
Unlike Northfield, but in common with most other grantmaintained schools, we have retained our integrity, by staying totally unselective, as well as our "street cred", by properly caring for the estimated 210 out of our 240 annual intake who are below national average in reading, numeracy and comprehension when they join us.
I also fall out with Jimmy McGovern over his treatment of the children. Like Drew, I cannot accept that virtually every child in every classroom is confrontational, surly or negative. Children are easy targets anyway, lacking as they do channels of suitable expression, and nowhere is this more explicitly illustrated than within the walls of Northfield School, where they are written off as another accident of the masses or downgraded to a subculture from which escape, even through the same avenue of education which has saved so many of us, is both impossible and unthinkable.
The drama of it all, though, is compelling, powerful and exhausting.
Hearts and Minds is an important and substantive contribution to the great educa- tional debate. To traditionalists, it will be regarded as another dangerous example of pseudo-documentary, while, to the trendies, it will be seen as virtual reality.
Yet the characters and events will strike a familiar chord with most parents and teachers who recognise that good drama, like a good school, is seen to be true to life because it is larger than life.
The writer is headteacher of Baverstock Grant-Maintained School, which is in an economically deprived area of Birmingham.