'Brightest girls' among physics A-level dropouts
Some of the brightest girls doing AS-level physics drop the subject without taking the full A-level, say teachers.
A teacher-run study is canvassing this year's students' attitudes to the subject and will track how many return for A2 physics in September.
Physics has a higher student dropout rate after AS-level than most subjects.
"It always upsets me when we lose them but the biggest upset is when we lose high performing girls," said study co-ordinator, Ronan McDonald.
Mr McDonald, who teaches physics at a London state school, said the study emerged from a discussion on an online physics teachers' forum.
Teachers want to know why girls are more likely than boys to drop physics, often despite getting better grades.
Exam board figures show a steep rise in the numbers of students of both sexes taking AS-level physics, from 36,258 in 2006 to 61,176 last year.
There has also been a significant rise at A2, from 27,368 in 2006 to 35,569 last year, according to data from the JCQ (Joint Council for Qualifications).
But the figures show physics loses more students than most subjects after AS-level and that girls are more likely than boys to drop the subject. By A2, the second year of A-level, only a fifth of physics students are female.
Last year, across all subjects, the dropout rate between AS and A2 was 37%.
In physics, the figure was 39.9% overall: 37.8% for boys but 46.7% for girls.
The puzzle for teachers is that girls, on average, achieve a quarter of a grade higher than boys.
"There is a clear advantage to being female to study physics: a greater chance of top grades and a lower chance of failure and lower grades. This holds at both AS and A2", says their preliminary paper.
Last year, a quarter (25.2%) of female candidates achieved an A in AS-level physics, compared with just over a fifth (21.4%) of male candidates.
The A2 grades told a similar story with 35.5% of female candidates achieving an A or A*, compared with 29.9% of males.
The survey asks both male and female physics AS students how their attitude to the subject has changed since they started the course.
Do they "love it", think "it's quite cool" or has it been "a mistake"?
Has the maths content of AS physics been "too challenging", "about right" or "a bit too easy"?
They're also asked to say whether they will keep the subject up for A2 and why.
Is physics too difficult, likely to result in their lowest grade, are they no longer interested or are they reluctantly dropping the subject?
Mr McDonald says he is also interested in the views of former physics A-level students.
One told BBC news she dropped the subject after AS "because of perfectionism".
Another, currently studying architecture, continued to A2 but said she had struggled at AS "because it was such a large group".
"There were 20 or 25 of us. It's hard to say you don't understand when it's a really large group.
"In A2 it was so much easier when there were only five of us. There was a massive dropout in my year."
Charles Tracy, head of education at the Institute of Physics, said some girls might find a very male-oriented physics A-level class "off-putting".
However, he said, in some ways the data was "reasonably positive".
"Some girls might want to study medicine at university and choose physics as a fourth subject to take to AS and we're glad that they're at least taking on some physics, even if not to the end of A2."