Ms Macdonald told the Institute of Physics Congress at the University of Salford that research showed girls from single sex schools did better in science than those at mixed schools and were more likely to carry on with science to A-level and at university.
Girls are now outperforming boys in science and technology at GCSE but only one in five A-level physics student is a girl and boys account for an even higher proportion of A-level entries than they did 10 years ago. Research published four years ago by the University of Bristol's department of education found that about half of girls who had been taught GCSE physics in all-girl classes went on to take it at A-level, compared with only a handful in previous years.
Eighty-two per cent in the single-sex classes achieved A to C grades, compared with a national average of 40 per cent.
Ms Macdonald, a former physics teacher, said: "Boys are more confident and vociferous than girls in a mixed environment and they tend to take over. Teachers will say that we need girls in mixed classes because they are a civilising influence. Does that mean we are prepared to sacrifice girls so that boys do their best?" Ms Macdonald said the problem of persuading girls to do physics had become acute now that nearly all British schools were co-educational.
"Girls do very well at GCSE. They simply choose not to do it at A-level because they don't feel comfortable. Girls like to feel they are approved of and as soon as they feel slightly intimidated by boys they back off.Boys are happy about taking risks and don't mind being wrong. They like to compete. Girls don't like being wrong, so they won't compete."
Girls needed to be reassured that they could do physics well, she added. At present, most pupils study "double award science", which includes physics, chemistry and biology.
Pupils do not know their mark for each individual subject, so girls tend to assume that their biology result has pulled their total mark up. Ms Macdonald argued that each of the three sciences should be graded separately. She added that all physics teachers should be given an expensive car to show that physics was a rewarding, prestigious career.
How The Sexes Compare
Exam Boys Girls
Entries 23,119 6,553
Pass rate 88.7% 91%
Entries 20,132 16,971
Pass rate 88.4% 90%
Entries 19,822 29,070
Pass rate 85.9% 88.4%
Source: 1998 A-level examstatistics for candidates aged between 16 and 18Reuse content