Media playback is unsupported on your device Media caption Physics teacher Claire Hamnett discusses how to break down the "gender bias" that seems to prevent many girls from studying science at A-level

Almost half (49%) of state-funded mixed schools in England are "reinforcing gender stereotypes" in terms of the subjects students study at A-level.

This is according to a report published on Monday by the Institute of Physics (IoP).

It says these schools are failing to counter the idea that certain subjects are for girls and others are for boys.

The institute is calling on schools to address the issue to avoid inadvertently limiting pupils' options.

The study used information from the National Pupil Database, which contains a record of students' A-level choices.

It looked at six A-level subjects, finding three with a very female-biased student base - English, biology and psychology - and three that are studied by many more boys than girls - physics, maths and economics.

The research went on to score schools based on how well they were doing compared with these already skewed national average ratios.

"We found that nearly half of the co-educational state-funded schools we looked at are actually doing worse than average," explained Clare Thomson, curriculum and diversity manager at the Institute of Physics.

"That means they're actually making this gender bias in terms of progression worse, rather than even meeting the national average."

Although the figures in this study are from a database of schools in England, the researchers say that similar gender bias is evident in Wales, Scotland and Northern Ireland, and that this is likely to be a UK-wide issue.

Unfair bias

Crucially, Ms Thomson added, the research showed that this bias was much less of a problem in single sex schools.

"So we really want those mixed schools to think about this issue and see if there are ways they can address it," she told BBC News, "because it means that it's unfair for the students who are attending those schools."

Some schools are bucking this trend.

Key findings Four out of five state-funded co-educational schools do no better than the national gender ratios for A-level subject choice. These average ratios are already very imbalanced

Single sex schools are significantly better at countering these gender imbalances

Schools with a sixth form have smaller gender imbalances

Independent co-educational schools perform better than state-funded schools, but there are far fewer of them

There are differences between regions and local authorities that experts say will require further research to explain Source: Institute of Physics

Cheney School, a mixed, state-funded school in Oxford, was one of 28 that received the highest score.

Head teacher Jolie Kirby stressed the importance of male and female role models, including teachers and outside speakers to inspire the students.

"[People are] willing to come into school and talk about their careers and experiences," Mrs Kirby told BBC News.

"We have a number of staff in school that come from quite humble backgrounds, and they're able to talk about how they've challenged stereotypes in their own lives.

"So I don't think it's about additional resources; I think it's about an approach that will work for students and young people and about bringing people into the school to help you with that."

And this does seem to be working.

One student, Emma, who is studying the very male-biased physics and maths at A-level, told BBC News: "It's never really occurred to me that, just because I'm a girl, I wouldn't be able to do these subjects."

Education Minister, Elizabeth Truss, said that physics and maths were "increasingly important for a wide range of careers from business to culture".

Responding to the report, Ms Truss told the BBC: "It is worrying that we perform worse than international competitors and this waste of talent is holding our country back.

"We are putting huge focus on raising standards in maths, physics and computer science to make sure these important skills are universal - and not just for boys."