Pupils at all-girls' schools are more likely to be bullied and violently attacked than at other kinds of schools, Government research has found.
Physical bullying is worst in female-only classrooms, with the problem escalating as children get older, according to the study.
More girls and boys taught in a single-sex environment reported abuse from other pupils, compared with the 90 per cent who attend co-educational schools.
By the age of 16, pupils at all-girls' schools are "significantly" more likely to be the victim of violent bullying than those at mixed schools or boys-only schools, researchers at the National Centre for Social Research found.
The study says bullying is "more prevalent in single-sex schools . There are different kinds of pupil dynamics in single-sex schools that lend themselves to a greater risk of bullying overall".
It continued: "Overall, girls in all-girls' schools were more likely to report being bullied than girls in mixed schools at the ages of 14 and 16, and boys in all-boys' schools were more likely to report being bullied than boys in mixed schools at the ages of 15 and 16.
"We found evidence that all-girls' schools in particular may be very different environments from mixed schools in terms of bullying, and that there are different risks in these schools which are related to different types of bullying and at different ages when compared with mixed schools."
The study also found pupils attending schools with higher proportions of children getting free school meals were less likely to report being bullied, and especially unlikely to report name calling.
But pupils attending schools with more special needs pupils were more likely to report being bullied and especially likely to report being called names. The researchers found being from a poorer home does not make children more likely to be bullied.
"An increased likelihood of bullying for pupils in schools with more pupils with (special needs) is of some concern, and may indicate that more attention needs to be paid to these pupils as potential victims," the report suggested.
"It may also indicate that these young people are potential perpetrators of bullying."
One headmistress of a girls' school commented: "I don't agree that girls' schools have problems with physical bullying. Girls are more subtle - they just exclude each other.
"They are also more likely to report bullying because they are more interested in relationships - friendships are hugely important and girls are much more sensitive. At single-sex schools, we have the advantage of focusing anti-bullying strategies much more specifically at one gender."
The researchers interviewed 15,500 children for the report.