Mary Jo Jacobi, adviser to two former American presidents, can spot a woman who has been to an all-girls school within 10 minutes of starting a conversation.
She believes confidence and ambition, two qualities that helped her rise from humble beginnings, come naturally to women educated at single-sex schools.
"Going to a girls' school makes a huge difference, mainly in a woman's attitude. After a 10-minute conversation with a woman I can tell if she's been there or not," she told the annual conference of the Girls' School Association, in St Andrews, this week.
Single-sex schools allow girls to develop their academic potential and give them self-assurance to deal with others, she said. They also develop the ambition, competitiveness, resilience and determination needed for girls to do well in life.
Miss Jacobi, who has a CV many a City high-flyer would be jealous of, should know.
Her parents were bakers in a poor southern Mississippi town, and could only afford to educate their five children privately by paying the fees partly in bread.
Now she sits on a plethora of boards and committees and in her day job, as vice-president for group external affairs Shell International, is in charge of crisis, reputation management and global communications for the oil giant . She has also acted as a special assistant for business liaison to Ronald Reagan and assistant secretary of commerce to George Bush Sr. To get on, you had to take risks, she said. Not enough women did so but those who went to girls' schools were more confident risk-takers than their peers from mixed schools.
The value of private education was touched on by many of the speakers at the conference.
In her opening speech, Pauline Davies, GSA president, said she backed the Conservatives' idea of a voucher schemeto give parents a subsidy of pound;3,500 to educate their children at any private school. Added to the association's commitment to provide more means-tested bursaries, this could mean more affordable private sector, "open to many more girls", said Mrs Davies, head of Wycombe Abbey school, a pound;20,000-a-year boarding school in High Wycombe, Buckinghamshire.
Mike Tomlinson, former chief inspector of schools who is leading a review of exams, told the conference he favoured replacing coursework with a single dissertation. He also wants more challenging questions in examinations and less assessment overall.
Heads were warned that society is in danger of creating a "rootless and restless generation". Mary Steel, head of St Mary and St Anne school, in Abbots Bromley, told the conference that many parents no longer valued community spirit and the need to do things for others. She said a selfish attitude, was being transferred to children. "We are in danger of creating a rootless and restless generation of young people who could end up circling around with no direction in life," she added.