An investigation is set to be launched into extreme variations in schools’ GCSE results which a headteachers’ leader said had left many teenagers as “victims” of the Government’s reforms.

Brian Lightman, general secretary of the Association of School and College Leaders, said some schools had received “surprising results” which had “shocked” them.

He said that the ASCL would be gathering evidence for an investigation into the results and leading schools are also considering action against the exam boards after seeing huge falls in their results.

A state grammar school which regularly tops exam league tables and one of the country’s leading independent schools joined comprehensives in disadvantaged areas in expressing fury over the results, particularly in English.

Overall, the percentage of top grade A* to C grade passes went up for the first time in three years from 68.1 per cent to 68.8 per cent. However, the overall pass rate declined from 98.8 per cent to 98.5 per cent and the percentage of A*s fell from 6.8 per cent to 6.7 per cent. The pass rate in different subject areas varied dramatically with English recording the biggest ever drop in the top grade pass rate in the history of the exam – going down from 63.6 per cent to 61.7 per cent. Results in maths, though, showed the opposite, increasing from 57.9 per cent to 62.4 per cent, beating English for the first time.

“We’re seeing volatility in a significant number of schools – in all kinds of schools,” said Mr Lightman. “It is the independents as well as the maintained schools.

“We’re seeing some surprising results which have shocked some schools. There are individuals [pupils] who have become the victims of these changes.”

He added: “It’s not just borderline C/D candidates not getting C grade. It’s also A rather than A* and remember that could mean Oxbridge or not, or Russell Group or not.”

“There are students who last year, or the year before, with the same work, might have got a higher grade. And if standards have been maintained (which exams regulator Ofqual says), then that should not be the case and that is a major cause for concern.”

Dame Joan McVittie, headteacher of Woodhouse High school in Tottenham, north London – singled out as a beacon of excellence in a disadvantaged area – saw her English pass rate plummet from 69 per cent getting A* to C grade passes to 52 per cent.

That meant its overall pass rate dropped from 62 per cent to 43 per cent – only marginally above the Government’s minimum target of 40 per cent. “I’m absolutely furious at the results,” she said.

“I don’t care about performance tables,” she said. “It’s about getting the students the qualifications they deserve.”

Her fury was echoed by Nicole Chapman, head of Chelmsford County High School for Girls, Essex, a grammar school regularly topping exam league tables, who added: “We will be taking issue with the exam boards concerning a number of subjects where results do not reflect the ability of the students.”

One leading private school also saw English results fall from 92 per cent to 77 per cent. Its head said: “English is just perverse this year. Something has happened with the marking.”

This year saw a dramatic fall in the number of early entrants taking the exam at 15 – down 39.3 per cent to 489, 190. In addition, in English, speaking and listening no longer counted towards the final grade, prompting scores to desert the GCSE for its international equivalent, Also, this year for the first time saw a move away from coursework to end-of-two-year exams.

Girls increased their lead over boys with 73.1 per cent getting five A* to C’s including maths and English compared to 64.3 per cent, meaning the gap rose by 0.2 percentage points.

School Reforms Minister Nick Gibb said the figures showed thousands more students were taking their GCSEs “at the right time”.

Aiming for Cambridge: The girl who couldn’t read

A girl who could not read or write until she was 10 celebrated top grade GCSE passes yesterday and is now contemplating a place at Cambridge University.

Holly Sayer, a student at the Charter Academy in Portsmouth, got 10 A* to C top grade passes, including an A* in English Literature and an A grade in English.

However, it was not until she arrived at the academy that she was diagnosed as dyslexic and began to read fluently.

“I didn’t learn to read and write until I was nine, 10 years old,” she said, “but that had been because I’d moved around a lot. I hadn’t really got a lot of schooling in.

“I’m quite heavily dyslexic. The only way I could get round it was through the extracurricular help I was given here. I kind of have the theory that if you want something then you go and get it.”

The Charter Academy is viewed as an outstanding model for tackling the performance of white working-class pupils.

Holly will now sit A-levels at the school after spending five-weeks at an award-winning school in the United States, the Phillips Exeter Academy, in New Hampshire.

The student is interested in becoming a film director.

Full marks: School’s record result

Pupils at Thomas Telford were last night celebrating their school becoming the first comprehensive to get a 100 per cent record at GCSE.

The school, which started life as one of the first City Technology Colleges, saw every single pupil obtaining at least five A* to C grade passes including maths and English.

Headmaster Sir Kevin Satchwell said the school had come close to achieving this target a few times since it became the first all-ability school in the country to achieve the Government’s original yardstick, in the year 2000 (five A* to C passes in any subject area).

“It seems a fitting tribute to the hard work of our staff and students that we’ve now actually done it – the first comprehensive to achieve this elusive target.”

The school is massively oversubscribed with eight pupils chasing every place.

It starts its pupils on GCSE courses when they first arrive, aged 11 or 12 and operates a longer school day than most with lessons starting at 8.30am and finishing at 4pm. Some pupils stay on until 6pm for extra teaching.