Girls do significantly better in single-sex classes, research claimed today.

The academics who compiled the research said that girls who showed less confidence in the classroom may also be less competitive in the job market.

The research was carried out on around 800 economics and business studies students at the University of Essex.

The research was designed to build upon the findings of earlier experiments with school-age pupils which showed girls were more willing to take risks and to be competitive when placed in single-sex groups.

Last year researchers Dr Patrick Nolen and Professor Alison Booth divided first-year undergraduates into three groups for introductory courses in economics - some all-girls, some all-boys and some mixed.

And while there was no effect on the exam scores of the boys' groups and the mixed groups, the girls' groups saw a 7.5% boost in their average marks.

A major part of that improvement was linked to attendance - girls were much more likely to turn up for classes if they were placed in single-sex groups.

On average, girls in single-sex groups attended 71% of the compulsory classes, while girls in mixed groups attended just 63%.

That explained about half the difference between their scores and those of girls in mixed groups.

However, the experiment showed that while single-sex classes for girls led to better exam scores, there was no significant effect on their coursework marks.

Dr Nolen, of the university's department of economics, said women and girls who were risk-averse might be less likely to compete for promotion at work in the future, and that could affect their chances of success.

"I would like to see policy makers think about this," he said.

"We should be investigating it and intervening pre-market in the environment in which students learn."

The university students were asked if they were willing to take part in an experiment, but were not given details of the research.

Student Corina Musat, 20, said that when she was placed in an all-girls' group she simply assumed there were more girls than boys on the course.

"I think the atmosphere was more friendly and we bonded because we were all girls," she said.

Undergraduate Emilia Matei, 20, said: "I think it was the best class I had last year.

"I don't know whether it was because it was a single-sex class or whether it was the teaching.

"In the all-girls' class, you didn't have to have that much courage to go to the blackboard and answer the question."

The earlier experiments on which this research was based were conducted with 260 teenagers from two girls' schools, two boys' schools and four co-educational schools in Suffolk and Essex.

They showed girls who went to single-sex schools were more competitive, even when they were in a mixed-sex environment.