Private schools hold 'open days JUST for grandparents (because they may be paying the bills!)

Older people who made money in the property boom are increasingly helping their own children pay boarding or day school fees.

Diana Watkins, deputy chairman of the Independent Association of Prep Schools, said: "As some prefer to do this covertly, I believe the number of grandparents paying is higher than most realise."

Julie Robinson, headmistress of Vinehall School in Robertsbridge, East Sussex, holds annual Grandparents' Days. Guests can attend an assembly, get a classroom tour and enjoy a cup of tea with teachers. More than 100 attended this year. Mrs Robinson said: "It seems to be a fairly new phenomenon. It's a chance to say thank you to grandparents who are helping out."

The trend highlights the difference between the financial health of a typical couple over 60 and that of their children.

Many economists believe that the over-60s hold a relatively high proportion of Britain's wealth - largely because they bought houses decades ago which have since rocketed in value. In contrast, their children - who are mostly in their 30s or 40s - are likely to be burdened with large mortgages and a higher cost of living.

A study published by HSBC in May this year has already highlighted the growing number of 'granny nannies', who are saving their children £50billion a year in childcare costs.

It is also believed that grandparents are having to help out more because private school fees have risen sharply in recent years, driven by a rise in teachers' pay.

The average cost of sending a child to boarding school is around £12,000 a year.

Julia Dalton, head of St Leonards-Mayfield school in East Sussex, said grandparents were more likely to pay school fees than five years ago - often using trust funds.

One of the country's top independent schools, St Paul's in West London, has also noticed the trend. High Master Martin Stephen said: "Grandparents prefer to spend their money on grandchildren than have it go to the taxman when they die."

Alison Callaghan, 33, of Marple, near Stockport in Cheshire, is considering taking up her mother's offer to help pay for a private education for her children.

Mrs Callaghan - whose husband Tom, 37, is a teacher - wants to send Jessica, six, and Jack, four, to an independent school but does not have the money.

She said: "My husband and I are very keen our children get a private education. It's certainly not a waste of money in our eyes. I imagine there are a lot of people in our situation getting help from their parents."