Boys should be educated separately during secondary school to avoid them being intimidated by girls, according to the new head of the Girls' Schools Association (GSA).
Alun Jones, president of the body which represents independent girls' schools, said separating them in state schools could prevent boys falling behind girls in exam results between the ages of 11 and 16.
He told the Sunday Times: "If you have a very bright, very driven, very focused, very articulate lady, which a lot of girls are, that intimidates a boy in the classroom, especially boys of average ability.
"The result is that boys don't put their hands up to answer questions or they indulge in immature behaviour to avoid being shown up.
"Boys will put their hand up if they feel safe; they won't if they are in fear of being ridiculed or humiliated. Boys fear failure just like girls do.
"In the most formative years when adolescence is hitting with a vengeance, boys should be educated separately. More single-sex classes for boys in state schools might halt the decline in boys' achievement."
He added: "I think that every state school should consider... experimenting with teaching boys and girls separately especially in subjects like English, maths and sciences.”
Fears of a gender gap have been fuelled by Department for Education statistics released in October which showed 61.2% of girls at state schools scored at least five C grades including English and maths last year, compared with 50.8% of boys.
But at A-level boys did better than girls with 12.3% of male students gaining three A*-A grades, compared with 11.1% of female classmates.