One in five British children cannot find the UK on a map of the world, a magazine's research suggests.
One in 10 children could not name a single continent
National Geographic Kids said it also found fewer than two thirds of children were able to correctly locate the US.
The magazine, which questioned more than 1,000 six to 14-year-olds, said it found several London children did not know they lived in England's capital.
Teachers' union the NASUWT said the findings were "nonsense" and did not reflect staff and pupils' hard work.
National Geographic Kids also discovered 86% of the children interviewed failed to identify Iraq and one in 10 could not name a single continent.
Boys seemed to show a slightly better geographical knowledge than girls, with 65% able to locate a number of countries around the world compared with 63% of girls.
Scottish children appeared to be the most geographically aware with 67% able to point out the most countries, out of England, the US, France, China and Iraq, on a world map.
Professor Alan Smithers, director of the Centre for Education and Employment Research at Buckingham University, said the findings were "rather frightening".
"These results underline the need for education to concentrate on the essentials.
"How are children going to be able to get as much out of their life if they fail to have an understanding of the shape of the world?"
The Department for Education and Skills said geography was a compulsory subject on the National Curriculum for five to 14-year-olds.
A spokesman said all 14-year-olds should be taught to use atlases and globes, as well as learning about places and environments in the world.
Chris Keates, general secretary of the NASUWT, said: "The constant desire for groups to produce statistics to do down the English education system is quite appalling and does nothing to recognise the excellent work of children and staff."
The magazine carried out the study to mark its UK launch and highlight "gaps in children's geographical knowledge".
Environmentalist David Bellamy said the world was still an undiscovered place for many children.
"Making geography fun and exciting is so important because it makes children aware of the importance of caring for the environment and, by learning about the world, it helps bring other people's worlds and cultures closer to their own."