Yesterday, veterans of the second world war and their families gathered on the Normandy beaches to utter the famous vow of remembrance: "At the going down of the sun and in the morning we will remember them."

However, a new survey shows that fewer and fewer children are remembering anything about British history. In fact, a considerable number even seem to have developed a touch of false-memory syndrome when it comes to our recent past.

The poll found that: 22% of under-16s don't know if their family members were involved in the second world war; 13% of children learn about the second world war from films or computer games; and 27% of children under 16 aren't bothered if stories about their family's war experiences are forgotten.

Most incredibly, some 13% of under-16s think world war three has already happened.

The nation's leading historians have reacted with shock to the survey. They warned that ignorance about the second world war, and the past in general, creates serious problems for both today and the future, and pointed to schools marginalising history as a possible source of the problem.

Many fear that the teaching of history in Scottish schools is being downgraded. Some secondaries even rotate geography and history teaching, so that pupils get geography in one term and history in the next.

"It just takes your breath away," said acclaimed historian Andrew Roberts, author of The Storm Of War, a new history of the second world war, which is published in August.

"How can people not be interested in what their family did in the war? It seems to fly against human nature to not show at least some curiosity about something like that.

"Families sharing stories is vital. It is not always objective when it comes to history, you'll find a lot of grandfathers saying they won the second world war single-handedly, but what it does is spark a general interest. A healthy interest in the greatest events of our times is an absolute prerequisite to make informed decisions today."

The survey, which was commissioned by battlefield holiday specialist Leger Holidays, should not surprise us, according to pre-eminent Scottish historian Tom Devine. Teenagers are suffering from "a growing historical amnesia", he says.

"At the family level, knowing its history means a sense of belonging," he said. "And then within a national level, at an ethnic level, it is what gives them an awareness of where they've come from and who they are. So if this amnesia becomes extreme, it will create cultural disorientation. But the way modern society is going, it would not surprise me."

He said this amnesia was being brought about by "the continuing marginalisation of history being taught in schools, so it only reaches a minority of pupils".

But British veterans' groups said the survey and claims of "amnesia" about the second world war among teenagers did not marry with their own experiences.

The Royal British Legion of Scotland said young people have "never been so interested or generous". It said the biggest supporters of the annual poppy appeal came from the 15-26 age group, and school visits to battlefields are booming.

"There is always going to be a regrettable percentage, even if it is as high as one in five, that doesn't know or care," said spokesman Neil Griffiths. "But the numbers show the people who do care are increasing."

"The poppy appeal went through a lull in the 1960s and 1970s, largely because children of the veterans were bored to death about dad going on about his war stories. But the grandchildren were fascinated. And we are seeing that as a phenomenon of modern history education. People are delighted to discover about their grandparents in the war."

Jock Dempster from Dunbar has five grandchildren and two great-grandchildren. In 1944, as a 16-year-old, he set sail from Greenock with the merchant navy to deliver supplies to the Russian port of Murmansk.

Now 81, he tells his tales of Arctic convoys, Germans chasing him by sea and air, rough seas, frozen wastes and appalling conditions on board, to his family and groups of schoolchildren.

He too believes that young people are interested in hearing about the second world war.

"Their wee eyes just light up," he said. "When they see you with medals on Remembrance Day, teenagers come up and chat. The first thing the young lads ask is, how many Germans did you kill?', but they are genuinely interested. They want to know how cold it was, what the Russians were like."

He added: "It is important they remember though, and the stories are told. It shows them the futility of war. A wee boy asked me once, Why didn't the war finish when Hitler was killed?' That's a good point."