Girls achieving top grades in science and maths at GCSE are deterred from continuing to a higher level with such subjects, including physics, because they are affected by low confidence and an absence of peers in the classroom, research has found.

As hundreds of thousands of pupils await the results of the GCSE exams on Thursday, a study, published by the Institute for Fiscal Studies, suggests that only dramatic intervention will change girls’ low take-up of physics and maths at more advanced levels.

About 90% of GCSE results in England this year will be awarded in the new reformed subjects first taught two years ago. This change has meant a far greater emphasis on exam marks in deciding final grades, likely to improve the relative performance of boys.

But the IFS study notes that while girls have long outperformed boys at GCSE level, including in the science, technology and maths subjects known collectively as Stem, fewer girls go on to take maths and physics at A-level, and fewer continue with those subjects at a higher education level.

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Girls are therefore missing out on potentially highly paid careers. Women with maths degrees earn 13% more than other female graduates five years after university; women with degrees in economics, which require high levels of maths ability, earn nearly 20% more.

In a pilot study investigating why girls are under-represented in maths and physics, the researchers interviewed nearly 300 girls across 40 schools predicted to achieve at least grade 7 or A in maths, physics or combined science at GCSE. The study also had focus groups of girls in Bolton, Hull, Birmingham and Portsmouth.

The study offered girls financial scholarships in return for studying physics or maths A-levels, but the rewards made little difference.

“A substantial proportion of the girls responding to the questionnaire felt that no amount of money could induce them to study maths or physics,” the research found. “These girls suggested that talks from female role models in Stem, Stem work experience and interventions to build girls’ confidence in maths and physics could be more effective in encouraging them to study maths and physics.”

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Low confidence appeared to be a big barrier to taking physics. Of all the girls surveyed who were expected to get grades 7-9 in maths or sciences, equivalent to A-A* previously, 50% said they agreed with the statement: “I often worry that it will be difficult for me in physics classes.” The figure compared with just 25% saying the same for the study of maths.

The survey found that fear of being among a small number of girls studying the subjects was also a big barrier, with 67% agreeing that “Stem jobs are male dominated”. Girls in the smaller focus groups said that “male dominance and boys’ behaviour in the classroom” were reasons for not taking Stem subjects at A-level or university.

But while the take-up of Stem subjects was better at all-girls schools, the fact that girls there still lagged behind the proportion of boys taking the subject suggested peer involvement was not the sole factor.

Sarah Main, executive director of the Campaign for Science and Engineering (CaSE), said the results showed the need for the government to collect and analyse more data on the issue. “It’s great that we are getting a light shone on this problem but honestly my heart sinks when I read this research. These are very talented girls, doing very well at maths and science, and they still think they’ll struggle doing physics.”

Main said that recent improvements in the numbers of girls taking maths and chemistry at A-level showed that the problem was not insoluble.

CaSE has recommended that the government makes a serious effort to improve careers guidance, and sets out a strategy to improve take-up and diversity of Stem subjects. “That way you could tackle the problems of confidence and isolation, and motivate young people from all walks of life to take these subjects,” Main said.

The latest GCSE results are expected to show more pupils taking physics, chemistry and biology as separate subjects, propelled in England by the government’s promotion of its English baccalaureate suite of subjects.

Biology and chemistry entries, in particular, have had a rapid increase this year, becoming some of the most popular optional subjects at GCSE level.

The exam results in England are now mainly graded under a new system, the marking scale of 9 to 1 replacing the A* to G letter grades.