Boys really do find it harder to learn to read than girls, according to a study involving more than 10,000 pupils.
They are twice as likely to be poor readers, says a paper from the Institute of Psychiatry at King's college, London, Christchurch school of medicine, New Zealand, and Warwick university, although the paper said more research was needed into the possible cause of the gender gap.
Researchers said the findings refuted the myth that teachers are more likely to identify boys as poor readers than girls.
A 1990 study in the United States, led by Professor Sally Shaywitz of Yale university, said that although research identified no significant differences in reading ability between 400 seven or eight-year-old boys and girls, schools were referring between two and four times as many boys as girls. This suggested teachers were biased against boys.
The latest paper cites four large-scale studies. It also analyses data previously collected on children in New Zealand and the UK.
It points out that a Programme for International Student Assessment (Pisa) study - which compares the achievements of 15-year-olds in 32 countries - found that in all countries girls are more literate than boys, although the size of the gender gap varies.
Professor Robert Goodman of the Institute of Psychiatry and co-author of the research, said: "The Shaywitz study has been very influential in making people feel that it is due to gender bias that teachers or schools or clinics find more boys than girls with reading difficulties. Our study has found teachers have been right all along and that there are more boys with difficulaties."
Co-author Dr Julia Carroll of Warwick university said: "As reading disability in childhood is associated with adjustment problems in later life, there is a definite need to recognise sex differences."
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"Sex differences in developmental reading disability: new findings from four epidemiological studies" Journal of the American Medical Association: Vol 291; no 16