Making the grade: The Kent school pupils who are leading the way for thousands of others

Schools in Kent are failing, says the Schools Secretary Ed Balls, and he isn't going to stand for it. Twenty-two schools are still not meeting his target of having 30 per cent of their pupils getting five good GCSEs including English and maths, so he is sending in advisers to sort them out.

The move has roused fury among headteacher, who point out that, using the Government's own statistics, many of these so-called failing schools are in fact doing an above-average job in a system in which one-quarter of pupils are creamed off into grammar schools. In addition, they say, some eastern parts of the county are among the most deprived areas in the country.

Paul Carter, leader of Kent County Council, is definitely "not amused" and has written to the Schools Secretary to say that GCSE results for Kent are above those in comparable areas, and that a pioneering vocational curriculum has led to declining numbers of young people in the county who are neither in employment or training.

"Our primary school achievement levels are below average but our results at Key Stage 4 are way above, which gives you some crude measure of the value our mixed economy of secondary schools add to their pupils' progress," Mr Carter says. "There is no community in the county where the results for 16-year-olds, taken together, show less than 40 per cent getting five good GCSEs. The curve of improvement in our schools over the past five years has been astonishing. There are five or six schools I'm still worried about, but we are already intervening and supporting them."

Mr Balls is unrepentant, however. Selection can be no excuse for failure, he says, pointing to the spectacular success of one school in east Kent as an example of what is possible. King Ethelbert has 750 pupils aged 11 to 16 and serves a poor, white, working-class area outside Margate on the Isle of Thanet. It has a troubled history, and in 2008 just 14 per cent of children got five good GCSEs, including English and maths. Last summer, the school was "named and shamed" as part of the Government's National Challenge programme, which targeted poorly-performing schools, and was linked up with a grammar school, Dane Court in neighbouring Broadstairs. Paul Luxmoore, the head of Dane Court, came in as executive head, with Kate Greig simultaneously appointed as the new head of King Ethelbert's.

Then came a whirlwind of activity. Pupils were told their school might be closed unless their results improved, parents were involved, staff were supported and new teachers were appointed, with extra money channelled into the school through the National Challenge programme. Children's performance was tracked in minute detail and that data was used to offer carefully-targeted support.

"The help was unconditional in my case, especially in English where I really struggled," says Keisha Pile-Gray, who got 10 good GCSEs and is now taking A-levels in a neighbouring school. "It was ridiculous. Everyone else believed in me apart from me."

Another former Year 11 pupil complained that he could have papered his bedroom with the letters sent home about his coursework. On results day last summer, everyone, including dinner ladies and cleaning staff, held their breath to see if the school had made it. It had. Thirty-four per cent had achieved the necessary five good GCSEs, the school was the second-most improved in the country, and improvements are continuing apace. Already, 27 per cent of Year 11 students have passed their maths GCSE, and many pupils are taking English GCSE this autumn in an effort to improve results and hit the National Challenge target early.

But the real success is the way the school has begun to create a culture of achievement in which pupils feel valued and motivated. "The teachers push us, but in a good way," says Rachel Buckley, 14. Paige Seager, 12 , says that if you are stuck the teachers help you by giving you clues. "But they encourage you to work independently at the same time," she adds.

Pupils agree their teachers are "brilliant". There is always someone to talk to about problems, and there are clubs and study sessions after school, including the chance for older pupils to work with pupils from their partner grammar school. "A rising tide carries all ships," says Mr Luxmoore. "The Year Sevens have higher expectations because of the previous year's results."

But if Mr Balls is a fan of King Ethelbert's, no one at King Ethelbert's is a fan of the way he uses targets to drive school improvement – or his finger-pointing at Kent schools. "We were horrified by his statement," says Mr Luxmoore. "It targets schools in a way that is utterly unfair. The reason why Kent has so many National Challenge schools is because this is a selective system. Ed Balls has had that explained to him a thousand times already."

Even when King Ethelbert was getting only 14 per cent of pupils to the GSCE benchmark, he points out, it was still among the best in the country for adding value to pupils' performance.

Teachers concede the National Challenge threat brought everyone together and channelled much-needed extra resources into the school. But despite last year's spectacular jump in results, they say real improvement is a long, committed hard slog that had already started before the national programme was created, and will continue after it disappears.

"Everyone at this school has worked their socks off, and done incredibly well," says Ms Greig. "Kent advisers have been absolutely superb and Kent County Council has supported us in every possible way. What we've done here is to change the culture of the school. But that's not to do with National Challenge. It's to do with is creating good teams and letting them get on and create the opportunities for children to do as well as they can."

Elsewhere, the National Challenge has been an instant success, with a 40 per cent drop in the number of schools not meeting minimum standards in the first year. But critics say the threatening way it has been implemented, along with the short-term nature of extra money it brings, could mean its effect is temporary.

John Dunford, general secretary of the Association of School and College Leader, says: "The money is going to disappear just at the same time as general funding for schools takes a downturn because of the recession and this is bound to have an effect on schools, especially those that have taken on extra staff."

Government sticks and carrots, it seems, might make schools jump in the short term, but in the end nothing substitutes for long, hard graft.