Single sex education has no benefit for girls, according to the headmistress of one of Britain's leading girls' schools.
Fiona Boulton, head of Guildford High School, said girls perform just as well in mixed classrooms as in lessons surrounded exclusively by females.
In an interview with the Telegraph, she criticised the 'narrow focus' of some all girl schools and said teachers should be concerned with getting 'the best out of every pupil' irrespective of gender.
The Girls' Schools Association insists that girls perform better when taught alone, giving them more confidence to thrive without being pushed into stereotypically female disciplines.
But Mrs Boulton, whose school is currently ranked among the top 10 in the country for both GCSE and A-level results, said she was not interested in 'talking about all girls, which is such a narrow topic'. She said: "I think if you create a really great environment then pupils do well. I don't sell a school on it being single sex... I sell it on the fact that we set out to be excellent in all that we do and that's why you should choose us – not because it is an all girls school."
Asked if the benefits of single-sex schooling were overblown, Mrs Boulton said: "Personally, I do, yes."
She added: "I think there are lots of divides in this country. We talk about independent v state, boys v girls – they are all children. We just need to work out how to teach children and how to get the best out of each child rather than which school they are in."
She continued: "It is about education and how to raise standards, how to get the best out of every pupil, rather than talking about all-girls, which is such a narrow topic.
"Yes, I educate girls. But we are an outstanding school because we set out to be excellent in everything we do."
Alice Phillips, president of the Girls' Schools Association, said: "Many of the top performing independent schools in the country are girls' schools."
She added that an analysis of A-level results for all girls in all schools and sectors shows that those belonging to GSA were more likely to score highly in subjects such as science, technology, engineering, maths and foreign languages.