Overall, pupil numbers in private schools fell by 1.5 per cent over the past year, lower than expected, according to the annual census of the Independent Schools Information Service (Isis), whose members educate 80 per cent of fee-paying pupils.
But the fall in boarding is much larger. The census finds a 6.7 per cent drop in the numbers of full-boarding boys, and 5.4 per cent for girls - the biggest fall since Isis began compiling figures 11 years ago.
Many private schools have been coping by encouraging more weekly boarding, whereby children return home every weekend. However, even weekly boarding numbers are significantly down - a 9 per cent fall among boys and 3.6 per cent for girls.
Isis said that boarding places were the main victim of recession, but the figures clearly show the main cause of the boarding slump is that parents are turning against boarding young children. At the ages of seven, eight and nine, numbers fell by 12, 17 and 15 per cent respectively last year. By contrast, at 13 and 14, numbers declined only 2.7 and 4.4 per cent respectively.
Joan Jefferson, president of the Girls' Schools Association and headmistress of St Swithun's in Winchester, insisted that boarding 'is not in a state of terminal decline'. The Isis report argued that the outcome could be a stronger but slimmer boarding sector.
Cost is a further factor. Average fees this year have risen by 8.7 per cent - roughly three times the rate of inflation. However, Michael Oakley, secretary of the Independent Schools Bursars' Association, said that fee increases this September were expected to be lower - averaging between 4 and 5 per cent.
He added that much more money was being put into funds to support the fees of children with less affluent parents. One in four pupils now receive some help with their fees and the total number of pupils receiving fees assistance has more than doubled since 1982.