The school where the headmaster Philip Lawrence was murdered five years ago celebrated a turnaround in its fortunes yesterday.

St George's Roman Catholic school in Maida Vale, west London, saw the number of pupils getting five top-grade GSCE passes rise by nearly a half in a year – and for the first time every pupil who took the exams this year got at least one pass.

The number of pupils achieving at least five A* to C grade passes – the marker by which schools are traditionally measured – went up from 13 per cent to 20 per cent, lifting it away from the level where it could face the threat of closure for low standards. This was the first real concrete sign of exam success since Mr Lawrence died at the school gates after going to the aid of a pupil who was being assaulted in December 1995.

The results are a fitting end to the reign of Dame Marie Stubbs. The 61-year-old grandmother, who was brought out of retirement a year ago to turn round the school, is leaving later this month.

Dame Marie took over at the school in March last year. The institution was closed down for a week after an assault on the previous headteacher and another member of staff. At that stage, it was on the hit list of schools compiled by Ofsted, the government's education standards watchdog, after failing an inspection.

Yesterday, though, the playground was buzzing with the noise of enthusiastic pupils collecting their GCSE results and looking forward to going on to college or to a sixth form at a neighbouring school.

Dame Marie said: "It's a lovely sight to see. It's a nice way to bow out, too. Last year we had six per cent who got nothing at all from their GCSEs but this year 100 per cent got at least one pass."

The achievement is a significant one for the school. Nationally, just over 2 per cent fail their GCSEs, with the figures higher in inner-city school. But the leap in the number of pupils with at least five top-grade passes may be more significant for the school. By rising to 20 per cent, the school has passed the 15 per cent target the Government set for all schools to achieve by next year.

Under the plan drawn up by David Blunkett, the former secretary of state for education, any school failing to achieve this target by then can be closed or given a "fresh start", with its name changed and new staff taken on in a bid to bury a past of failure.

Dame Marie said: "To achieve a 50 per cent increase in five A* to Cs is a significant achievement when you consider this was a year when we were battling against special measures [being included on the list of failing schools] and inspectors were around the place all the time. This is a start, and maybe the school can go and get it up to nearer 30 per cent over the next two years.

"I'm very happy and relieved at what has been achieved. It's a great day for the staff of the school and the pupils. They are being rewarded for all the hard work they have put in. The figure of 100 per cent getting at least one pass is a crucial one; it shows that everybody who put in for the exams has got something to show for it," she said.

The success means that many of its pupils will now be going on to study A-levels – including its star pupil, Tariq Kamel, who achieved 11 A* to C grades and won a scholarship to an independent college. This year's success is also being seen as a boost for St George's plans to set up its own sixth form, a move that would increase the school's popularity with parents in the community.