There are 75,000 boys and girls in independent boarding schools in the UK (and a much smaller but not insignificant number in maintained schools). The market in independent boarding has been shrinking fast over the last decade. The number of boarders has fallen by 30 per cent since 1988, and in that period 73 boarding schools have closed or been forced to merge. Despite the efforts of the recently founded Boarding Education Alliance, there is little chance of the market recovering.
The leading boarding schools for boys, such as Winchester and Eton and, for girls, Wycombe Abbey and Cheltenham Ladies College, are still in demand because they are outstandingly good schools, but many other boarding schools are desperately seeking Susans and Simons whose parents are prepared to fork out pounds 15,000 every year after tax. New markets in the Far East provided a temporary stay of execution for the weaker schools, but the Asian economic crisis means that even that source of customers is drying up. At the end of the millennium the boarding sector is wondering whether it has a future at all.
The heyday of the British boarding school was roughly the hundred years between 1850 and 1950. During that period those parents who could afford to do so sent their son to boarding school because they were convinced that only boarding could develop those qualities that he would need to make his way in the world. In our post-modern society, a list of those qualities may provoke a cynical smile. "We may rely on the boarding school boy," wrote a Marlborough College master in the Thirties, "to place the team before self, to remain faithful, to stiffen the upper lip when the need arises and to keep his standards of integrity unsullied in the face of temptation.'
Whether boarding school really did develop those qualities is open to question, but what mattered was that the parents thought that it did. They were prepared to pay fees not necessarily for good academic results, not for their own convenience, not even for the social cachet of the boarding school - but for the development of their son's character.
The motivation for sending middle-class girls to boarding school was more concerned with educational opportunity than with character, but the great boarding school headmistresses were confident that it was only in a boarding context that the right intellectual, moral and social attributes could be fully developed.
It is that confidence the heads of boarding schools seem to have lost. Headmasters in particular are very reluctant even to use the word "character," let alone suggest that their schools might develop different and, by implication, superior qualities to day schools.
The heads defend boarding on the grounds that it suits busy parents and that it provides more time for out-of-school activities. They recommend boarding schools on logistical grounds rather than philosophical or idealistic ones. Boarding schools are hostels for the convenience of parents, an alternative to day schools only in the sense that the pupils stay the night.
This lack of confidence in the intrinsic value of boarding poses a greater threat to the future of boarding schools than escalating fees or the collapse of the Asian market. If parents only pay boarding fees because it suits them, rather than because boarding offers a distinctive education, the market will always be unstable.
The heads of day schools, particularly those that dominate the upper reaches of the A-level league table, are not particularly sympathetic to the boarding schools' dilemma.
For generations independent day schools were regarded as inferior whatever their academic record because no day school was regarded as a proper public school. They can be forgiven if they now enjoy a little schadenfreude as some of the former aristocrats of the independent sector struggle to justify their existence.
The challenge for boarding school heads is to present a convincing case for the added value of a boarding education. The convenience of busy parents is not irrelevant but it should not be the sole raison d'etre for boarding. The increased time for out-of-school activities is not irrelevant either. As Vicki Tuck, the principal of Cheltenham Ladies College points out, it gives more girls more opportunities to find out what their interests and aptitudes are. That is a plus, but it still falls short of a confident belief in the unique value of a boarding education. Many good day schools have an equally diverse programme of out-of-school activities.
The heads' problem is made more complex by the negative image that boarding still has, despite the sweeping changes in boarding school lifestyle. Parents still worry about bullying, even though your child is just as likely to be bullied in a day school - more likely, perhaps, because the law has persuaded boarding schools to be ultra-vigilant.
Heads concentrate on dispelling the negative image and reassuring parents that Flashman left a long time ago; their prospectuses are full of happy, smiling faces and emphasise the importance of the individual, not of placing team before self.
However, the special educational value of boarding escapes them. The headmaster of Milton Abbey School has at least attempted to pin it down. He proclaims that "what we do best is citizenship" and argues that what children learn in boarding school "will in adult life translate into social responsibility".
If that is true, it could be the added value the boarding school heads are looking for.
But they will have to prove their case because parents and day school heads will be sceptical of the idea that boarding school pupils become more responsible citizens.
Dr Rae, a former head master of Westminster School, is the author of 'Letters to Parents' (HarperCollins)