The son of an acquaintance of mine has recently landed a good job on a national newspaper. For the past few months I've been reading the articles written by this boy – let's call him Derek – and thinking how delightfully original they were. Last week I ran into Derek's mother and told her that her son was brilliant and that she must be proud of him. She rolled her eyes and said he hadn't always been a star. He had been expelled from his state comprehensive school at 15, failed dismally academically and had spent his teenage years off the rails. So how, I asked, did he land this most sought after of jobs, one that Oxbridge graduates kill for?

She said that Derek had decided in his early 20s that he wanted to be a journalist and simply refused to take no for an answer. He more or less took up residence outside the newspaper of his choice, bombarding it with e-mails, until eventually he was allowed in as an unpaid intern. He financed his journalism by working night shifts as a hospital porter, until eventually he was offered a job.

We all love an underdog story, and this one vastly cheered me up. All the more so because it seems to belie the conviction of every pushy parent that if a child puts one foot wrong academically they have blown it for life. Both in London and New York there is this feverish notion that the journey to success starts at around three years old. It is vital to get a child into the right nursery school that will get them into Harvard or Cambridge or wherever. And if the child does not land up with straight A grades then clearly their chances of success in life are very low indeed.

This tiresome hysteria has got worse in one generation. When I was at school and at university there was a lot of opportunity for screwing up, and most of us availed ourselves of it at one point or another. In fact, if you cruised effortlessly from one academic triumph to another you were regarded as rather dull. As a schoolgirl, not only did I fail to get straight As, I didn't get any As at all – though I did get an F and even a U (for unclassified).

Having failed in a small way – though not as impressively as Derek – I like to think it does one good. It means one then has to work like a dog to catch up, and that one may have a fresher way of doing things.

The day after I bumped into Derek's mother I picked up a copy of The New Yorker and saw an article labelled Highly Effective Underdogs by Malcom Gladwell. He argues that the underdog has power that the favourite lacks, and the source of this comes from the two things that I presume Derek has – an appetite for work and a disregard for doing things the normal way.

Gladwell tells the story of how a basketball team of little blonde 12-year-old girls beat the champs because they played differently and worked harder at it. He concludes that it's a myth to think David hardly ever beats Goliath; he wins all the time.

Hooray, I thought as I started to read the article. But as I went on, a nastier thought occurred to me. The theory may be heartwarming and we can all point to our own pet examples of 12-year-old girls or boys such as Derek to make it feel true. The only problem is that it isn't true – it's claptrap. The reason these examples cheer us up so much is because they don't accord with real life: they are exceptions, freak-shows and fairy stories. In true life David doesn't win all the time. He loses, again and again.

In two of the most sought after professions – law and journalism – Goliath has always done well, but recently has been enjoying a winning streak. According to a recent report from the Sutton Trust, there is even more dominance by Oxbridge and private schools in some of the top UK professions than there used to be. The sad truth is that the pushy parents are being quite rational – even if boring and tiresome – to obsess over the qualifications that their children get. Being on the winning side helps one win even more than it ever did.

The only area in which David routinely wins is when he decides not to compete at all, but to set up his own business. The businessmen Sir Alan Sugar and Sir Richard Branson famously failed at school and so had no choice but to go it alone.

Otherwise, if one wants to see David thrashing Goliath one has to take refuge in reality television. Sir Alan, an underdog himself, last year picked as the winner of The Apprentice TV series Lee McQueen, a man whose qualifications were so dismal he had to lie about them. This underdog won the battle for audience ratings; whether he will go on to any further success is debatable.

Though it is depressingly rare for the underdog to win in the real world, I'd like to cling to the idea that when they do, they have something special to offer that the overdog does not.

I was talking to a politician about it last week and he said that all the researchers he hired were top graduates except for one – who had left school at 16.

I asked hopefully: was he different? More original? Harder working?

The politician shrugged. They were all bright. They all worked extremely hard.

So, no difference at all?

He thought again. There was a difference, he said. The guy who left school at 16 had a great big chip on his shoulder.