Boys have caught up with girls on reading ability, according to a study into the book-reading habits of school children.
What Kids are Reading 2012 found that the difficulty level of books read by boys is no longer generally lower than girls.
The report, written by Professor Keith Topping of Dundee University, analysed what more than 210,000 British primary and secondary school children are reading for pleasure.
Roald Dahl was the most popular children's author, closely followed by Roderick Hunt, author of the popular Magic Key series, according to the study. Harry Potter author J.K Rowling came fifth in the list.
There have long been concerns that boys lag behind girls in terms of ability.
But researches discovered that across the one-11 school years, there were four years where boys were reading more difficult books than girls, three where girls were choosing more challenging titles and two where it was equal.
"We can no longer claim that boys read at a lower level of difficulty than girls so overall under-achievement must be caused by other factors," the report said.
The study used computer software to analyse what difficulty level of books children are reading.
It found that the average book difficulty rises as students get older, but not in proportion to the rate at which students reading should be improving.
After Year 9, researchers discovered that the average book difficulty attempted by children declines.
Mr Topping said the finding was more positive than previous reports, in which the difficulty declined after Year 6, but called for more improvement.
"If the older readers challenged themselves more, better reading outcomes could be anticipated," he concluded.
From August 2010 to July 2011 2,886,920 books were read by children in 1,237 schools, the report, funded by Renaissance Learning, found.
Jonathan Douglas, director of the National Literacy Trust, said: "We know that reading for pleasure strengthens a child's reading and writing skills and has a significant long-term impact on their education and life outcomes.
"A young person who has the experience and habit of reading for pleasure has laid the foundations for lifelong learning."