Britain's top head bares her soul

he head of this country's top independent school is a feisty and attractive woman in black knee-boots and a flippy skirt. This should not come as a surprise, but somehow it does, and there are even still visitors who mistake her for a secretary. "But I don't mind that. I've never minded going against the grain."

In fact it is clear that Katy Ricks is her own person the minute you enter her study, at Sevenoaks School, in Kent. Gone are the old curtains and chandeliers. In has come minimalist decoration in grey and shocking pink, with polished oak boards and a bare, floor-to-ceiling window. She hesitated about spending money on the refurbishment when she arrived at the school four years ago, "but then I do spend practically 12 hours a day in here, and when people come in they can look around and see that this is me!"

It is early on an autumn morning and, outside the minimalist window, mist and dew are coating the school's campus as 980 pupils head for their lessons. Although the school was founded in the 15th century, it was as a lay foundation without either chapel or school hall. As a result, it looks less like an ancient public school than a sprawling New England liberal arts college, which, somehow, seems fitting for its unique academic profile.

The school is well known for pioneering the international baccalaureate (IB), and when the Universities and Colleges Admissions Service decided to draw up a points tariff for the IB as well as A-levels, Sevenoaks came out well on top of the independent-school league table, with a remarkable point score of 587.9, equivalent in A-level terms to four grade As and a B for every pupil. Last year 48 pupils got Oxbridge offers, and 95 per cent of leavers got a first or second choice university.

"But I think that should probably be topp, with two 'P's, like in Molesworth," says Ricks, eager to seem modest about the achievement. "I think it's good that we have two or three different league tables, all of which measure different things."

Like Sevenoaks itself, she has always gone about things her own way, taking up teaching because she so loved being at school herself. At her north London primary school she got both old-fashioned formality and liberal creativity. She had to learn poems by heart, but also did plenty of drama and music - "it was the time when the Inner London Education Authority was handing out free instruments to primary schools." Camden School for Girls followed, which had "a very strong ethos, aspirational without being stuffy. There was no uniform, so we all tramped around in flares and clogs, but it was made clear to us that there was no question but that we could do what we set out to do." Then came studying English at Balliol College, Oxford, another highly academic institution that shunned formality. "Although loads of Prime Ministers have come from there, it is not hung up on ancient tradition."

Three years of an unfinished DPhil followed before she started to look around for a job that was as much like being a student as possible, and fell into teaching English at St Paul's Girls' School, in London, introducing bright girls to Dickens, Lawrence and Pope. "I was completely unqualified in every respect, but if I was in the room with pupils I seemed to be able ask the right questions and to make them enthusiastic. I wasn't planning a career, I was just following what I loved, but I found it was brilliant fun."

By then she was married, and her classicist husband was finishing his doctorate in Birmingham, so she moved to teach at King Edward's School, where she was one of only three women on a staff. After that came Latymer Upper School, in London, then St Edward's School, near Oxford, where she was head of English, and got some boarding-school experience under her belt.

"But my husband was at King's College, and commuting, and we felt we needed to live in London again, so I then spent five years as one of the three deputy heads at Highgate. The school had 1,000 pupils, aged three to 18, and I really got to see how a big organisation works."

At 45, she has no children herself, and is clearly devoted to what she does. She may not have planned a career, but once in teaching she knew exactly where she was going. Early on in her working life she had listened to Heather Brigstocke, the redoubtable former high mistress of St Paul's, talking about how she had become a head after being left a widow at 30 with four children to care for. "And I remember thinking: 'I'm going to do that.'"

Her challenge was to find the right headship to apply for. Although much of her experience had been in boys' schools, she knew one of them would think twice before appointing a woman head, so she looked for "a co-educational school, near London, which was strongly academic but not hidebound by tradition."

Sevenoaks was the perfect fit. It had always been maverick, going co-educational early, pioneering community service for all students, and developing an international profile. She had no doubts about the rightness of the school for her, worrying "more about whether they would think: 'She hasn't been a head before. Will she know what she is doing?'"

It seems that she does. Although fees can go up to more than £20,000 a year, parents still queue to get their children in, and parents mostly see Ricks as an energetic and capable head who means it when she says that her door is always open to students, although a few fret that she could be making the school more academic and pressurised than it has been in the past.

From this year the school has ditched A-levels altogether and all 420 sixth-formers are taking the international baccalaureate, but Ricks says this has already brought benefits. "It has put a spring into the step of both students and staff. Now everyone is part of the same outcome. It's one diploma, not separate departments, like you have with A-levels."

She says that a balanced education is what the school is all about - "it runs six days a week, full on, with everything from jazz bands to the year-eight philosophy club" - and her immediate jobs are to consolidate the IB move, to oversee the building of a new sports complex, and keep the whole complex show on the road.

"I would certainly like to stay here, and I feel if I can retain enthusiasm and not get stuck in a rut then there's no reason why not. But, at the same time, I also feel that, in a way, a head's role isn't about making a mark, and that it's the sign of a healthy institution that anyone should be able to step in and do the job."