‘Plain Janes’ are often happier at school than the girls who seem most popular and attractive because sociable and successful pupils often have the worst problems, said Professor Carrie Paechter, from Goldsmiths College in London.

“There is a lot of pressure to be top of the social group, but often girls who are popular aren’t well liked - they’re feared because they’re dominant,” the Daily Mail quoted her as writing in a speech to be given at the Girls’ Schools Association annual conference in Liverpool.