Girls' schools have gone from looking fuddy duddy and unfashionable to being flavour of the month with parents - helped by impressive exam results and some pretty speculative psychology.
The numbers of single sex schools has dwindled in both the state and independent sectors but so appealing is the notion that girls and boys respond to separate teaching styles that headteachers have been experimenting with segregated classes in mixed comprehensives.
Pressure from some Muslims to separate girls has given the bandwagon a further push.
But there is no evidence for it, says Alan Smithers, professor of education at Buckingham University and one of Britain's most respected educational experts.
Flying in the face of a huge amount of parental gut instinct he concludes that 50 years of research "has not shown any dramatic or consistent advantages for single-sex education" for boys or girls.
People think single-sex schools are better because they do well in league tables, says Prof Smithers, director of the Centre for Education and Employment Research.
"But they are generally independent, grammar or former grammar schools and they do well because of the ability and social background of the pupils," he insists.
Even the apparent role of girls' schools in encouraging their pupils to take up science is disputed by Prof Smithers who points out that the proportion of girls taking physics went up between 1960 and 1985 - the time that single sex schools were disappearing.
His study, commissioned by the (largely co-ed) Headmasters' and Headmistresses' Conference of independent schools, has been flatly rejected by the Girls' Schools Association, an important voice in the private sector.
Brenda Despontin, president of the GSA and headmistress of Haberdashers' Monmouth school for Girls, says they support diversity and choice for pupils and parents. "But we cannot support the claim that gender is not an issue in education. Girls' schools allow pupils to develop in their own way - girls and boys learn differently and mature at different rates.
"If students seek the best grades, there is irrefutable evidence, from the Department for Education and Skills, that attendance at a single-sex school results in a better performance academically.
"Last year both boys and girls in single sex independent schools received 10% more A grades at A level than their co-ed counterparts - undeniable, statistically proven success which has nothing to do with selection," she adds.
