By an extraordinary fluke however, he is accepted into Briarcrest, a private high school that offers a fine Christian upbringing for the offspring of the city's white, God-fearing and overwhelmingly Republican establishment. One of these families literally picks up the boy off the streets, takes him into its opulent home in the best part of town, gives him a new life and ultimately adopts him. The school has no special sporting traditions, and our hero has no evident interest or aptitude for sport, or for that matter anything much else in life – least of all learning.
But, as a result of the indefatigable support and love of his new family, he makes good enough grades to graduate from high school, win a college football scholarship and embark on a career that takes him to the fame and riches of the National Football League. Such is the true story of Michael Oher, and Hollywood has made a film about it that has just opened across the US.
The release has of course been carefully timed. This week America celebrated Thanksgiving, the perfect moment for feelgood movies about random acts of kindness to strangers, the overcoming of adversity and rose-tinted endings. The Blind Side is also about football (of the American variety) and makes its debut just as the college and NFL seasons enter their decisive phases. Last and not least intriguing, the film is a window into the most foreign of Americas, a South haunted by race and steeped in the twin religions of Bible belt Christianity and the brutal sport of football.
Michael Oher's saviours are Sean and Leigh Anne Tuohy, a poster couple for the New (and these days thoroughly Republican) South. He is a former basketball star at "Ole Miss", the University of Mississippi, who now owns a chain of fast-food restaurants, while Leigh Anne runs her own interior decorating business. "Who'd have said I'd have a black son before I met a Democrat," muses Mr Tuohy at one point, summing up his existence in a world poised between the redneck and the country club.
But altruism alone would not have produced a story fit for Hollywood. For that, "Big Mike" had his size and a remarkable speed of movement to thank. The boy-mountain might have had no special interest in football and his gentle disposition could not have been more at odds with the take-no-prisoners savagery of the sport. But whether he liked it or not, he had the perfect physical shape for it.
The Blind Side is based on the book of the same name by Michael Lewis, a former bond trader and now author of, inter alia, Liar's Poker – to this day the funniest book written about Wall Street – and Money Ball, a study of shrewd financial management in baseball. Lewis excels in coming at a sport from an unexpected angle, and he did so again in The Blind Side which appeared in 2006, when Oher was already a star player in his second year at Ole Miss.
The term "blind side" refers to the area where the quarterback, the key player on the team, is most vulnerable to being caught (or "sacked" in football parlance) by a behemoth defender on the opposing team, before he has got rid of the ball. To block this behemoth and protect its quarterback, a team needs an even larger and faster behemoth of its own. Most quarterbacks throw with their right hand, so the biggest danger comes from the left. Thus the importance of the offensive left tackle. Oher might not have realised it, but capricious nature had created in him one of the most sought-after commodities in American professional sport.
In describing his attributes, Lewis waxes almost mystical. "The ideal left tackle was big, but a lot of people were big. What set him apart were his more subtle specifications. He was wide in the rear and massive in the thighs. He had long arms ... and giant hands: when he grabbed a defender, it meant something."
And that is not all. "The ideal left tackle also had incredibly nimble and quick feet. He had body control of a ballerina and the agility of a basketball player." Oher would prove such a superman. "He looked like a house walking into a bigger house," said a football talent-spotter as the young man squeezed through a door to meet him. "There's the big-blob 300-pounder, and there's the solid kind. He was the solid kind."
Hollywood, of course, takes the odd liberty with the facts. Amazingly, Quinton Aaron, the actor who plays Oher, is – at 6ft 8in and 380lb (more than 27st) – even larger than the real thing, who was a mere 6ft 5in and 350lb in his high school days.
Measured against Lewis's book, the role of husband Sean Tuohy is somewhat understated. In the film, his wife runs the show. The South has its steel magnolias but few as titanium-plated and glamorous and as capable of giving such motivational speeches as Leigh Anne in the persona played by Sandra Bullock. The Tuohys have a son, but the real Sean Jnr cannot be as freckled and cartoon-cutesy as the maddening little boy on the screen. And then, of course, there's the syrupy musical score, making sure the mandatory lump in the throat is duly raised.
Some US reviewers have found the mixture cloying and condescending. A classic essay in white guilt, one wrote. The New York Times complained about how little serious attention is given to the violent and dysfunctional background from which Oher is escaping, how the film "is interested only in that world as an occasion for selective charity". Another critic tartly noted how American films about sport "have a long, troubled history of well-meaning white paternalism, with poor black athletes finding success through white charity." In this respect The Blind Side succeeded merely in finding "a new low".
Maybe. But for this foreigner in the audience, at least, such shortcomings were more than compensated by the light thrown on the cut-throat billion-dollar business that is college football – nowhere more so than for the dozen colleges that make up the Southeastern Conference, covering the heart of the old Confederacy. There, the football coach with his seven-figure salary and country club membership and private jet thrown in is arguably the most important figure on campus. When word comes of the prodigy of Briarcrest, to a man they flock to watch him. Whether or not the phrase "I hear that kid can really pepper the gumbo" was actually uttered by Ole Miss's head coach Ed Orgeron in real life as well as in the movie, doesn't matter. In The Blind Side the coaches play themselves, smooth tongued and blazer-clad, ready to push the rules to the limit to secure the services of a player who could turn a good team into a championship winner.
Indeed, the tensest scene in the film is when a bureaucrat from the NCAA, the body that runs college football, interrogates Oher, suggesting he might have been illegally steered to Ole Miss: that his adoptive parents might have taken him in not out of Christian goodness, but in order to make sure their alma mater got the hottest offensive tackle prospect for decades, not one of its hated rivals.
And in the ferocious universe of college football recruiting, such skullduggery is all too easy to imagine. But not in this tale, with "happy ending" written over the very first frame. This summer, Michael Oher was picked in the first round NFL draft by the Baltimore Ravens, signing a five-year, $14m (£8.5m) contract. "I don't believe what I just saw," was the immortal line of a great American sports commentator, apropos of a sensational game winning home run in the World Series baseball by an injured hitter who was not even expected to play. The film of The Blind Side inspires a similar feeling. But, a few Hollywood frills excepted, happen it did.