Teacher Diane Wilson put this dramatic improvement down to the school's study support centre where pupils can revise, do homework, or take part in educational clubs and activities during lunch breaks.
In 1990, the 1,200-pupil school took part in a pilot study support project organised by the Prince's Trust and evaluated by Professor John MacBeath, director of Strathclyde University's Quality in Education Centre.
The results of the pilot were so impressive, the trust decided to try to establish a network of study centres for secondary pupils in deprived areas throughout Britain. It held a conference at London University's Institute of Education this week to promote the concept.
Professor Peter Mortimore, director of the institute, told the conference that according to one estimate, 47 per cent of pupils in England are underachieving, and for some groups the figure may be even higher. "Staff and governors need to consider how best schools and parents can help young people to make the most of their talents."
Study support groups fit well with many of the findings from school effectiveness studies of the past 20 years, he added.
The idea certainly seems to have taken off at Sarah Bonnell School, in the London borough of Newham, where the majority of pupils are Asian or Afro-Caribbean and around half qualify for free meals. Owing to the centre's popularity, staff have had to extend the original large open space in the upper hall where pupils may sit and read or work on computers.
There is now a quiet area for younger children, a separate area for pupils in Years 10 and 11, and extra space for clubs, including reading support, educational games, and a debating society. Two members of staff are on hand to help with homework or GCSE coursework difficulties.
"The original idea was to provide a quiet area for students because many live in poor, cramped housing and don't have space to study. Others have a lot of outside responsibility such as looking after younger siblings and don't get much opportunity to work at home," said Ms Wilson, who manages the centre.
"However, it has proved enormously successful and it's got to the point now where the girls keep putting forward suggestions for things they would like to see developed. The whole ethos of the school has improved.
"Students feel there's support for their studies and value the centre as a useful resource. No one is forced to come here and the students appreciate it more for that," she added.
The Prince's Trust was giving money to around 150 schools, and a further 1,500-2,000 had either bought its study support pack or contacted staff for advice.
Nicola Mackereth, the trust's study support assistant, said: "We want to raise the profile of study support and get the backing of central government. The scheme is all about improving standards by reaching young people in danger of failing."
The trust was hoping to persuade other organisations including businesses and local education authorities to put in money too. British Telecom had sponsored the programme from the outset.
"Last year we gave out Pounds 55,000-worth of awards to 55 study support centres. A year later, we asked the schools if Prince's Trust funding had helped them get further sums, and a high proportion said it had," Ms Mackereth said.
Sazeda Natha, 16, and Shazea Ahmed, 15, intend to take nine GCSEs next summer and use Sarah Bonnell School's study centre most days.
Sazeda said: "It's helpful at exam times because you can revise with other people. Also, I already do about three hours' homework a night and I'd probably run out of time if I didn't get something done during lunch breaks.
"My little sister, who's 11, prefers doing her homework here because it means she can play with her friends in the evenings. Every school should have one."