Dulwich High School in south London is surrounded by expanses of smooth green playing fields. There’s only one problem - none belongs to the school.

The school for 414 boys is a little glass and concrete island of comprehensive education in a sea of privilege; the playing fields, swimming pools and tennis courts are the property of the prestigious independent schools in the area.

Dulwich High has been made famous for all the wrong reasons - it was the boys’ school that Social Security Secretary Harriet Harman controversially rejected in favour of a grant-maintained selective education miles away. Now it is supposedly one of the country’s worst schools after being named by the incoming Labour Government in May along with 17 other long-term underachieving establishments.

The headteacher, Lloyd Marshall, is indignant that his school has been pilloried, as he sees it, in order to embellish the Government’s tough stance on educational failure.

“The naming and shaming was totally unnecessary and unhelpful; I’m really sick and tired of the awful climate of hostility and negativity my staff have had to work under. I just wish people would be aware of the context and give my staff credit for the amazing work they have done.”

This summer, his pupils managed a substantial leap in their examination performance, with 22.5 per cent gaining GCSE grades A-C compared with just 9 per cent last year. This is still well below the national average, but it is a respectable percentage in the borough of Southwark (where the 1997 average is 26.4 per cent), and the rate of improvement is the greatest of the 18 failing schools on the list. “This is an im-proving school,” says Mr Marshall. “Now we have hard evidence.”

Earlier this week, Government inspectors paid what will be a decisive visit to the school, a final diagnosis of whether it is healthy enough to recuperate on its own, or whether it is fit only for a hit squad or closure. A “fresh start’’ does not seem feasible because it has already had one - formerly known as William Penn school, it was renamed and relaunched last year.

Verdicts on all 18 schools are expected early in November.

Like the other “shamed” schools, Dulwich High was given expert assistance from a “help-squad” or SMART (special measures action recovery team). Dulwich’s team turned out to be one man, Gus John, a former director of education in Hackney (a borough which got its own help squad three weeks ago after a damning Ofsted report on its education service).

Mr John’s report, together with the inspectors’ opinion, will be crucial in deciding whether the school will escape execution.

His conclusions are critical but not damning. Provided pupil numbers do not fall any further, “the school has a future so long as it is able to rigorously address the key issues and to harness a massive store of goodwill, hard work, commitment...”

These “key issues” are challenging ones: a minority of the staff are “totally unsatisfactory”, the school is being used as a dumping ground for excluded pupils from all over south London, and behaviour, staff appraisal and the role of senior managers are all problematic. But the overall verdict is that despite the bad publicity, this is an improving school rather than one that is spiralling into despair.

One hopeful sign is that 73 pupils entered Year 7 this September compared with 45 last year. Dulwich High’s inability to attract pupils has been one of its most intractable problems, forcing it to take the pupils rejected by others. These children’s behaviour and poor performance further detract from the school’s reputation and its ability to attract promising children.

Mr Marshall sees it as a moral duty to make the best of the children who come through his door, whoever they may be. “For many years the school has been used by some parents as an opportunity to place their sons who have got into trouble elsewhere, and we offer the chance for children to restart their education. The majority complete it successfully, but it uses up a lot of energy and resources.” So does teaching the basics - it is not unusual, he says, for 70 per cent of 11-year-old arrivals to have reading ages of below nine.

Dulwich High has its strengths. The richness, technical fluency and sophistication of the pupils’ art is more what might be expected of students than children in a failing comprehensive. But art is not high on the national agenda.

While Mr Marshall is happy to concur with the ideal of “excellence for everyone” and even “zero tolerance of failure”, he takes issue with what he sees as the Government’s lack of realism and narrow definition of success.

“The idea that in a school like this you’re going to have 80 per cent getting top grade GCSEs - it’s not going to happen. Some will, some won’t. There are different types of success. I believe every child can achieve at something, but it won’t necessarily be at exams. They should be congratulated on that, not criticised.”

Like most of the staff, Mr Marshall is proud of the school and full of plans for the future, despite working under the shadow of the axe. In about four weeks they will know if that axe will fall.