Girls from single-sex schools do better at science than those in mixed schools, while boys do better in mixed classes, physicist Averil Macdonald told the institute's annual congress.
Ms Macdonald, an educational consultant and physics lecturer at Reading University, said: "It is often argued that mixed classes are better because girls have a civilising influence on boys. But surely that just means we're prepared to sacrifice girls' potential to let the boys do their best?" Providing physics teachers with expensive cars would signal that science - and particularly physics - leads to prestigious careers, she said. "The Government's pound;5,000 bursaries for trainee physics teachers are a waste because students will take the money and run. Company cars would be a more effective way of showing teachers and pupils that physics is valued."
Teaching methods were only part of the problem, however.
GCSE science candidates are not given enough credit for achievement in the separate sciences, she warned. It is important that pupils know how well they have done in physics, often seen as the hardest discipline, she said.
"If we can remove some of the factors that hinder girls' success, then perhaps, one day, more women will share the joys and challenges of a science-based career and the UK's scientific and technical achievements will benefit from a greater pool of expertise," she added.