If you only had More House to go on, it would be hard to believe that boys’ schools were in crisis. The school is oversubscribed and headmaster Barry Huggett is pressing ahead with plans to let numbers “gradually grow” each year. Only last September, the school opened a suite of new science laboratories, a sign of its confidence in the future.

But beyond the leafy back lanes of Surrey that are home to More House, the picture is not so rosy. Boys’ schools are in retreat, with numbers falling sharply in recent years. It may be just a matter of time before it is only the likes of Eton and Harrow that are flying the flag for boys’ schools.

The situation has reached a point where the editors of the Good Schools Guide spoke earlier this year of the “near extinction” of independent boys’ schools, describing those remaining as “the survivors” of the tide of co-education.

Fewer than 5 per cent of schools listed in this year’s 25th anniversary edition of the guide, a compendium of the country’s top schools, are independent boys’ senior schools, compared with 24 per cent in the 1986 inaugural edition.

According to the Independent Schools Council, a quarter of all boys’ schools have gone co-educational in the past 10 years, and the number of boys in a single-sex establishment has dropped by a fifth in the same period.

Among the “fallen” that are now taking girls are many illustrious names such as Marlborough, Rugby, Wellington and Repton. Others, such as Westminster and Charterhouse, take girls in the sixth-form.

Although the number of girls’ schools has also declined in the same period, the fall has been nowhere near as steep. “I think society has changed,” says Janette Wallis, senior editor at the guide. “Looking for a boys-only school is seen as a bit old-fashioned.”

At More House, they have so far managed to resist the tide, although it is not for lack of interest, at least among the boys themselves.

“I have a school council and every year they ask, `Why can’t we have girls?’ and every year I say it’s because we have enough boys,” says Mr Huggett. “The move towards co-ed in the independent sector has been predominantly an economic one, but we are oversubscribed.”

Mr Huggett has no objection to co-ed schools in principle, but there is another dimension that weighs against the school admitting girls. All the pupils at More House have a learning difficulty - dyslexia being the most common - and Mr Huggett believes these boys do better in a single-sex environment. “They will be more at ease without girls,” he says. “They will be able to make mistakes without girls giggling at them and it takes some of the pressure off.”

This perhaps gives More House, the largest school of its type in the country, some protection from the move towards co-ed schools. But not all boys’ schools are in this position. At St James Senior Boys’ School, in Ashford, Surrey, headmaster David Boddy says they rely on their ethos to continue to attract pupils.

“Boys’ schools need to make it pretty clear that the kind of education they have to offer is distinctive and there are certain virtues in single- sex schools,” he says.

These virtues include not having to compete academically with girls, he says. St James is a non-selective school and, based on a belief that boys develop later than girls and have different learning styles, he suggests boys could be intimidated and so underperform if they are constantly measured against girls.

But Mr Boddy, incoming chairman of the Society of Headmasters and Headmistresses of Independent Schools, believes the school’s appeal is not just academic. He says parents are attracted by its promotion of “old- fashioned” values and by the spirit that is created in an all-boys environment.

“Many parents want their sons to be in male company and grow up as men,” he says. “The virtues of courage and strength and uprightness come to the fore in the company of other boys.”

He argues that the absence of girls makes boys more willing to embrace these values. “In the presence of another chap, a chap might be prepared to put his head above the parapet and speak out,” he says. “In the presence of a girl, particularly in puberty, they are not so willing to step up to that role.”

St James is undeniably helped by having a sister school for girls. Many of the remaining boys’ schools are in this position, such as St Paul’s and Haberdasher’s Aske’s. This offers a convenient solution to parents with both sons and daughters, as well as providing ready-made opportunities for the two sexes to mingle, through drama, music or debating societies, for example. This helps to satisfy parental anxieties that their progeny’s social skills will be stunted by a single-sex environment.

But confining these contacts to extra-curricular activities avoids boys being distracted by the presence of girls, Mr Boddy says. “To mix the genders is a bit like mixing fire and butter,” he says. “Inevitably you get something happening.”

Despite the wider malaise affecting boys’ schools, he says St James is thriving. From about 280 pupils seven years ago, it will have 350 next year. As well as its own virtues, it may be benefiting from the fallout of the switch to co-ed: with fewer all-boys schools around, those remaining become more sought after.

Jane Horrocks had not set out to look for a boys’ school for her son Dylan, now 13, but was won over both by the ethos at St James and by Mr Boddy’s arguments in favour of single-sex education.

“It allows them to focus more without the distraction of girls,” she says. “It also boosts their confidence, because girls are so much further ahead at age 11 and they don’t have to try to compete with girls.”

She says far from missing out, her son benefits from being in an all-male environment. He has developed an interest in sport that he never displayed at his mixed junior school and has retained an innocence that his peers in co-ed schools have already lost, she adds.

But, according to the statistics, there are increasingly few parents of like mind, and More House and St James are becoming very much the exceptions. Janette Wallis at the Good Schools Guide suggests that, for a boys’ school, admitting girls is not only a response to parental demand, but can create it. Admitting a cohort of high-performing girls can also move a school up several places in the league tables.

“It is a way of increasing numbers at a stroke,” she says. “It is also a way of improving academic results at a stroke.” The majority of parents who call the guide for advice are looking for a co-ed school. Among those looking for an all-boys school, the choice is becoming increasingly thin.

Girls’ schools have been less likely to go co-ed, partly because they tend to be smaller and have less good facilities, so taking boys would be unrealistic, Ms Wallis says. Admitting boys to a girls’ school would also be a harder sell to parents than taking girls in a boys’ school. And boys themselves may be less keen on going to a girls’ school than the other way around. “It is a much bigger thing for a girls’ school to announce it is going to start taking boys,” she adds.

David Boddy at St James is in little doubt about the reasons many boys’ schools are now taking girls. “Too many of them are chasing league-table glory,” he says. He believes these schools have been seduced by the idea that girls will boost their exam results, making them more attractive to parents.

The fact that these schools are independent has not made them immune from the league-table pressures facing state schools. The result, he says, is that rather than making the most of their freedoms, even private schools are becoming increasingly homogenous.

He says some parents have suggested that St James could take girls in the sixth-form, but Mr Boddy remains opposed. “We are pretty much of the view that single-sex education is the way forward for us,” he says. “I’m 155 per cent confident that we will carry on as an all-boys school.”

Brad Adams, director of the International Boys’ Schools Coalition, says that those left standing need to be “on top of their game”. He suggests the decline in boys’ schools in the UK may be partly a result of historical factors: there were more of them, and they carry class connotations. While boys’ schools in the UK are associated with entrenched privilege, co-ed schools are seen as progressive.

These issues do not apply in many other countries, he says, where boys’ schools are relatively healthy. “Internationally, there has not been the same winnowing out and decline,” he adds.

But the portents for boys’ schools in the UK appear gloomy. Geoff Lucas, secretary of the Headmasters’ and Headmistresses’ Conference (HMC), which represents many leading independents, says economic downturns often coincide with a shift to co-ed.

“Some people would argue that they do it for educational reasons or because parents are looking for greater integration, but the last time there was a serious recession (in the early 1990s) there was a big growth in boys’ schools going co-ed,” he says.

Mr Lucas suggests one consequence of this has been to reinforce the position of the remaining boys’ schools. “It has become a niche market,” he says. “It has reached the point that those schools that are left are very strong. I don’t imagine there will be much change now.”

Not everyone is convinced that the transfer from single-sex to co-ed is coming to an end, however. Andrew Halls, headmaster of King’s College School (KCS) in Wimbledon, south-west London, believes that after a period of stasis, the switch to co-ed may be on again. This is the result of both economic pressure and a smaller number of parents who went to co-ed schools themselves, he argues. “Among the younger generation of parents who are sending their children to independent schools, there is a less visceral belief in single-sex schools,” he says.

“I don’t think they (boys’ schools) will all perish, but I think we are now in a period of movement. I can see that in 20 years the default position will be co-ed.”

KCS itself is one of the latest to go co-ed, with 42 girls joining its sixth-form last September. Mr Halls says the decision was taken on educational grounds, but admits it made financial sense.

“The extra 40-odd pupils in the sixth-form has improved the bottom line,” he says. “Would we have done it if it hadn’t? Probably not. These are dangerous times and we need to consider the business logic of everything.”

He says boys’ schools often struggle to maintain numbers in the sixth- form: 16 is often the age when some boys want to move to a co-ed environment, while few boys of that age would swap a co-ed school for single sex. But he believes the presence of girls in the sixth-form brings educational advantages, allowing both sexes to benefit from the different approach of the other.

“If you had to choose an optimum time for girls and boys to work together, it is the sixth-form,” he says.

Many boys’ schools have introduced a mixed sixth-form as a precursor to going completely co-ed, but Mr Halls insists that this is not his intention at KCS. “It is certainly not part of my philosophy,” he says. “I know it has happened in many schools but I don’t see that as inevitable.”

For those that have switched, the “diamond” approach has become a popular option. These schools admit girls into the junior school and sixth-form, but the secondary phase is boys-only.

That was the approach taken by the Perse School in Cambridge, which admitted girls into its sixth-form in 1995 and then into its prep school in 2007. But the “diamond” school proved to be a staging post, and by September 2012 the Perse School will be completely co-ed.

Edward Elliott, the headmaster, insists the decision was not taken on financial grounds. The school was oversubscribed when it was single-sex, although it is “even more oversubscribed” now. Nor does he believe there are compelling educational reasons in favour of either single-sex or co-ed establishments.

Instead, he says it is the social benefits that have made him a believer in co-ed schools. Learning together helps dispel the myths the sexes have about each other, he says. “My own view is that academically it makes no difference whatsoever, but socially there are huge advantages,” he says. “It makes a big difference to all-round development. That is where you see the gains.”

The Perse’s decision to go completely co-ed surprised others in the single-sex world. As it has a sister girls’ school, a model that has provided some protection to boys’ schools elsewhere, it was assumed to be likely to remain single-sex.

But Mr Elliott suggests that boys’ schools are increasingly being seen as an anachronism, an accident of history, formed when boys’ education was more valued than that of girls. The Perse School was founded almost 400 years ago, during the reign of James I.

“Society has moved on and people see the advantages of what we are doing,” Mr Elliott says. “If you were creating a school from scratch in the 21st century, you would not create a single-sex school.”

This social tide may end up sweeping all but a handful of boys’ schools into the co-ed embrace, according to Bernard Trafford, past chairman of the HMC and headmaster of the co-ed Royal Grammar School (RGS) in Newcastle since 2008.

Mr Trafford took his previous school, Wolverhampton Grammar, co-ed, and says in his 21 years in HMC he has seen the organisation’s make-up go from around a third co-ed to 80 per cent. “It’s been a huge change,” he says.

His experiences have made him a convert to mixed education - “It’s a much richer experience”, he says - to the extent that he would not have taken his present job if RGS were still single-sex.

“Once you have taught in a mixed school you feel there is something missing in a boys’ school,” he adds.

Although he says the decisions to go co-ed at Wolverhampton and RGS - which made the switch in 2005 - were not made on financial grounds, he agrees that it does not make business sense to exclude girls. Nor does he believe that single-sex education comes high up on the list of most parents’ priorities.

While some of the more entrenched boys’ schools undoubtedly have a bit of life left in them yet, he says the single-sex model is becoming a thing of the past.

“There are some incredibly powerful all-boys schools,” he says. “They are enormously strong, so why would they change? But I’m convinced that somebody starting a school now would not do it like that. It is perverse to exclude half the population.”

Across the city, however, someone is doing just that. Newcastle School for Boys (NSB) is one of the newest independent schools in the country, opening its doors in 2005. While single-sex schools across the country are in retreat, headmaster Chris Hutchinson believes they have a future.

He regards the decline of the all-boys school as a result of making convenience and the child’s own preferences the priorities in choosing a school. “We have discerning parents, who are asking which of these schools is the right one for their son,” he says. “In my experience, that critical question is not being asked as much as it was 20 years ago.”

While he says he is “no evangelist” for all-boys schools, he believes there are sound educational reasons for educating the sexes separately. Schools that have gone co-ed have done so on economic grounds, rather than educational, he says. “It is nothing to do with education; it is because they need more kids in the school to make it run better.”

NSB also benefits from the presence of three all-girls schools in the city. Parents who have chosen a single-sex school for their daughter are more likely to do the same for their son, Mr Hutchinson says.

Although the outlook for boys’ schools is far from promising, he says the school is determined to resist going co-ed. “There is no reason we should do that,” he says. “We passionately believe in our ability to offer a better overall education for our boys. We are going to stick to what we believe in.”

If past experience is anything to go by, it will only be the exceptionally strong boys’ schools that survive this recession. Those that are still standing when the music stops may succeed in cornering the market, but the signs are that gatherings of all-boys schools are going to be increasingly lonely affairs.

Original headline: A gender for change