The poor dears are too honest and direct for their own good, says Anne Barnes, the general secretary of the National Association for Teachers of English.
While girls pick up sackfuls of marks with rambling responses to exam questions, boys get straight to the point - a terrible error.
"Boys assume the examiner is asking a serious question and they answer it as directly as possible," says Ms Barnes.
"It doesn't get them many marks because they don't extrapolate or embroider in the way the markers expect.
"Girls, who in our culture are brought up to fit in with other people's demands, give much more long-winded, polite responses."
As things stand, boys are way behind girls in English at every stage of compulsory schooling. Last year's test results for 11-year-olds showed that only 48 per cent of boys reached the expected standard compared with 66 per cent of girls.
Anne Barnes, herself an examiner, says the problem is particularly notable in high-ability boys, who don't get credit for intelligent but short answers.
"It's a difficult balance," says Ms Barnes. "Girls go on too much. Boys however, haven't got the point. The questions are a game, and girls understand that. They want to please the examiner.
"I'd like mark schemes to emphasise the virtue of articulate writing in a short space."