Image caption Boys are generally thought to be more reluctant readers than girls

Many secondary school boys do not have the stamina to read beyond the 100th page of a book, research suggests.

Teachers also revealed that classics of English literature, such as those by Jane Austen, are putting boys off reading.

Some 70% of the 500 teachers surveyed for publishers Pearson said boys had switched off by the 100 page mark.

This is leading many teachers to ditch longer novels in favour of shorter books, it adds.

Teachers were asked to identify points where boys would switch off in class when novels were being read.

A quarter said that the interest cut-off point happened within the first few pages of a book.

Pleasure can't be taught. Pleasure can only be shared Frank Cottrell Boyce, Best-selling author

A further 22% said interest waned within the first 50 pages, while a further quarter identified the 100 page mark.

Nearly a third of the teachers questioned said boys were put off before the book had even been opened, if they saw it had more than 200 pages.

According to the research, Shakespeare plays including The Tempest, Macbeth and A Midsummer's Night Dream were particularly unpopular, as was Steinbeck's 1930s classic, Of Mice and Men.

The reluctance to read could partly explain the achievement gap between boys and girls.

Last year 85% of 11-year-old girls reached the expected level in English for their age compared to 76% of boys. In reading, the gender gap was even more stark at 79% for girls and 64% for boys.

According to children's organisation Unesco, the biggest single indicator of a child's future success at school is whether they read for pleasure.

The research is timed to coincide with the launch of a new series of books called Heroes aimed at secondary school pupils which aims to switch boys back on to reading and get them past the crucial 100-page mark.

'Crucial role'

Best-selling author Frank Cottrell Boyce, consultant editor on the series, said: "Pleasure can't be taught. Pleasure can only be shared."

He added that boys should be started on shorter books.

Jonathan Douglas, director of the National Literacy Trust, said its research showed that boys lag behind girls not just in literacy skills, but in the amount they read and in the extent to which they enjoy reading.

"This gets worse as children get older. This is a vital issue and one the National Literacy Trust is working hard to address. More needs to be done to engage boys' and building on their own interests."

He added that publishers had a crucial role to play in this.