I participated in a lively discussion about character education at Policy Exchange earlier this week. For those of you who don’t follow every twist of the education debate, the idea that ‘character’ should be taught in schools has gained a lot of traction in recent years. And support for it doesn’t divide along party lines: both Tristram Hunt and Nicky Morgan are advocates of character education.

By ‘character’, the supporters of this idea have various desirable traits in mind, such as tenacity, reliance and self-control. There’s plenty of evidence that a child’s possession of these qualities is a strong predictor of later success. To give just one example, children who perform well in the marshmallow test, whereby they are given a choice between eating one now or two later, do better at school, are more likely to go to university and less likely to go to prison. According to believers in ‘character education’, it follows that we should teach children qualities like self-control, particularly in primary school.

I’m a detractor, although not completely dogmatic about it. I have no objection to teaching character outside the classroom. But I draw the line at devoting valuable curriculum time to it. Why? Because character traits are inherited, not taught.

I’m not talking about moral qualities, such as honesty, compassion and altruism. It may be that these can be cultivated. I mean performance-enhancing virtues, like stick-to-it-ness and the ability to bounce back from defeat, what exponents of character education call ‘grit’. There’s a growing body of evidence that these traits are largely hereditable, that is, encoded in our DNA. If you exhibit any of these qualities, it’s overwhelmingly likely that your parents did, too. And insofar as a child’s upbringing has any impact on the emergence of these qualities, it’s the peers they associate with during adolescence that matter, not their teachers.

This was the finding of the American psychologist Judith Rich Harris, who spent years researching the subject and published her conclusions in a book called The Nurture Assumption: Why Children Turn Out the Way They Do. Her hypothesis — that nature not nurture is the main determinant of character — has been corroborated by other numerous research studies, not least a 2005 paper by John Paul Wright and Kevin Beaver entitled ‘Do Parents Matter in Creating Self-Control in Their Children?’ By studying sets of twins separated at birth, Wright and Beaver show that when it comes to qualities we associate with a lack of self-control, such as impulsiveness, ADHD and hyperactivity, the impact of a child’s upbringing is negligible. Children’s defining character traits are evident by the time they’re 19 months old, with parents and teachers having little impact on their development.

This flies in the face of the teachings of child psychologists and suggests there’s little we can do when it comes to correcting children’s character defects. You can see why people resist it, particularly conservatives, since it lets negligent parents and irresponsible teachers off the hook. It even calls into question the idea that prisoners can be rehabilitated. But we cannot ignore the facts just because they’re unpalatable. If desirable character traits cannot be taught, we shouldn’t waste time trying to teach them.

As with so many educational fads, the problem is the opportunity cost — the time you’re wasting on gobbledegook that could be devoted to teaching children genuinely useful things, such as the history of the British Isles. Numerous research studies have shown that the best predictor of academic attainment is how much knowledge children possess at an early age.

For traditionalists like me, that’s reassuring, as was the recent report by the Sutton Trust which found that the most effective teaching method is not ‘discovery learning’ or ‘group work’ but direct instruction. Unfortunately, educational theorists are rarely led by the evidence, even when the brand of snake oil they’re peddling includes teaching virtues like honesty and truthfulness. One of the conclusions of a piece of research I read recently is that a strong predictor of academic success are fine motor skills. In short, if you want to maximise children’s life chances, particularly children from chaotic family backgrounds, you’d be better off teaching them handwriting than wasting time on character education.