“IT’S QUITE COOL to be at a girls’ school.”

As a slogan it may lack a certain zip, but Rosanne Musgrave thinks it captures an interesting side-effect of “girl-power”: that, after decades when bright girls in girls’ schools longed to go off and be cooler at a boys’ school, they are now more content to stay put.

Undoubtedly single-sex schools are doing very well. This year’s A-level league table in The Times put girls’ schools in the top four places, beating grand boys’ public schools such as Winchester, Westminster and St Paul’s. The 200 heads of independent girls’ schools meeting next week in Rotherhithe for their annual conference might be forgiven for gloating.

Miss Musgrave - this year’s president of the Girls’ Schools Association and headmistress of Blackheath High Scool in south-east London - has taught in girls’ schools ever since she left her first teaching post at the mixed Latymer school in north London, in 1976. “I was very struck by how much subjects were divided by gender,” she says. “The boys did physics and English was perceived by many, including the head, as a girly subject.” Miss Musgrave, an English teacher who was equally talented at both arts and sciences, did not feel comfortable with that.

She moved on to teach at Camden Girls, then a comprehensive. She then became head of English first at the independent Channing School in Highgate, and then at Haberdashers’ Aske’s in Elstree, where she ended up as head of the sixth form, before finally moving to Blackheath in 1989.

Miss Musgrave is an evangelist for teaching. She went into it more out of a sense of duty, a 1970s desire to “give back”, than by long-held design. Once in, however, she never wanted to do anything else. When she is not rushing about being the association’s president, she still aims to teach an English lesson to most classes in most years, as well as running master-classes in Chaucer and workshops on creative writing in Year 7.

Nothing makes her more furious than parents who comment to a teacher, “oh, I think she can do better than that,” when it is suggested that their bright daughter might go into teaching (“It’s quite offensive, apart from anything else,” she exclaims).

One of her messages to fellow heads next week will be to try to rise above the “admin” and remember their purpose: to inspire their pupils.

A large, friendly, energetic figure, Miss Musgrave certainly does not seem bogged down in the “admin” herself, as she sits in her airy, well-ordered office or takes the visitor round the closely- packed senior school site, ranging from a grand Victorian house to a 1950s chapel, now converted to a music centre. A computer sits winking beside her large desk. She may have an 1880s printing press at home (a personal passion) but is also enthusiastic about new technology; so keen, in fact, that she has taken a qualification to prove her competence, and persuaded three-quarters of her staff to do likewise. Every sixth-former has her own e-mail address.

The only child of two RAF officers, Rosanne Musgrave spent much of her early life on the move and attended state primaries in south-east England and Germany before going to a boarding prep school in Somerset at the age of nine.

To this precocious child, more used to the company of adults than children, boarding school meant stability and the chance to make friends, many of whom she still knows.

Intellectual stimulation came later, at Cheltenham Ladies’ College and St Anne’s, Oxford, where she read Anglo-Saxon and joined the Union, the Victorian Society and much else. Post-graduate work in linguistics at Reading University followed, and a post-graduate certificate in education at London’s Institute of Education - not, perhaps, the intellectual high-point of her life but “teacher-training has come on an awful lot since then”. She gained a distinction anyway.

She thinks teachers should experience both state and independent sectors and is a strong fan of partnership. Blackheath is itself mixed socially, and has one in four girls getting help with the pound;5,500 fees. It is also involved in a Government-funded scheme with nearby Eltham Hill girls’ city technology college, examining the impact of the Dome on Greenwich.

Her training in English language has, she thinks, helped her to teach pupils to write and speak coherently. Girls at Blackheath high learn early on to express themselves in public, helping out with assemblies from the start of Blackheath junior at the age of four. And her experience has made her well aware of the need to encourage girls to take intellectual risks rather than just getting the right answer and then polishing it.

“One of the ideas I encourage here is not to do everything in rough - do the final copy straight away,” she says. “After all, if you’re a lawyer in a courtroom, you haven’t got time to do it in rough.”

Which makes her nervous about the changes happening to examinations, especially at A-level. Will the opportunity to take modules twice mean that conscientious girls repeat them to improve their grades, rather than moving on to something new?

She shares concerns about continuous examining and the ensuing pressure on extra-curricular activities. The prospect of exams always left little time for them in Years 11 and 13, she says. Now, she sees signs of reluctance to dance or play in a jazz band in Year 10.

And what of inspirational, off-syllabus detours? “In my lower-sixth at Cheltenham we did almost no A-level syllabus work,” she says, “but my goodness, we were taught how to read, to study, to think. My English teacher made us write a sonnet a day. Some of the sonnets may have been pretty awful but it taught us a lot about sonnets.”

For sixth-formers, she sees in current reforms the danger of the “tick-box mentality” - and of making sixth-formers’ lives an exhausting grind, just as many managerial and executive jobs have become all-consuming. “It will be very sad if we make sixth-formers young executives in the same way.”

Miss Musgrave herself works punishing hours, arriving in her four-wheel drive vehicle at the crack of dawn and leaving late.

But she is doing what she loves and clearly wants to inspire others to do likewise.