Professor Alan Smithers' exhaustive worldwide study of the benefits of single-sex schooling has revealed what many of us suspected: there aren't any. Single-sex schools score highly in league tables but, as Smithers shows, it is because many of these schools are grammars or independent. Here we have further evidence of the irrepressible dishonesty employed by those who seek to maintain - or to reintroduce - outmoded educational traditions. Hold a neo-Victorian model up as being likely to improve academic standards, manipulate admissions criteria so an improvement in results is inevitable, and then spend the rest of the year shouting about how successful your new wheeze has been. We live in a PR-infected world. Much public service nowadays consists less of doing a job, more of stating ad nauseam how well it is being done.

Smithers' findings mean we have yet another meaningless stock phrase to dump in the dustbin of unfunny jokes that populate much of the British education debate. "Single-sex education causes academic improvement," can be added to the hilarious "specialism drives up standards across the curriculum" gag currently making many staff at specialist schools choke on their lunch, and to that killer punch-line: "Improvement in results at academies is not down to manipulated admissions."

My own objection to the idea of single-sex schooling is probably overly simplistic, and revolves around the fact that it is unnatural. It engenders fear and distrust of a mysterious other. We go to co-educational nurseries, and to mixed infant and primary schools. And we do this happily and naturally, mixing with the other gender with ease. When we reach the age of 11, however, our education system can divide humans into two entirely distinct species.

Socially, this is almost as disastrous as educating different creeds in separate schools. Teenagers who have grown up in single-sex schools, boys or girls, are not able to act naturally around the opposite sex, perhaps ever. Any system that encourages half the population to be scared of the other half is idiotic by design. It stores up a well of misunderstanding that festers mockingly within us, having ruinous effects throughout the journey of our lives.

There has been some suggestion that single-sex schools are under increasing threat. Far from it - the education bill has provided for them to expand. Let me explain. Many girls' schools are considered to be successful, and as "successful" schools are to consider expanding, it is likely that many girls' schools will do so. Where their neighbouring school is co-educational, the creaming off of more female students will inevitably affect the gender balance at the co-educational school.

There are already parts of the country where supposedly co-educational schools have a gender balance of three boys for every girl. This does nothing for these schools' results, thereby further conferring on them "sink" status; and meaning more girls are recruited for their single-sex neighbour, so that eventually you are left with one school for high-performing girls, and another for the boys plus any girls who don't pass academic muster. This situation exists already, and will be exacerbated by the education bill.

Our children are more mature than many give them credit for, and can cope perfectly well with being in the same class as the opposite sex without turning into a raging sea of hormones. I taught an all-boys class in a mixed school last year. There were some benefits, but most interesting was the response of the girls who'd had the boys taken from their English lessons. They were passionate in their opposition. We need the boys back, they said, so that lessons are more lively, and they need us to help them.