A growing number of secondary schools are in danger of failing to reach the Government's minimum target for performance as a result of this Thursday's GCSE results.
The science pass rate is set to drop as a result of examiners making physics, chemistry and biology papers tougher in the wake of complaints that they were too easy.
In addition, maths is expected at best to be pegged at its present rate or even fall as thousands of pupils are put in for the exam a year early. Figures released by exams regulator Ofqual showed 90,000 candidates sat the exam a year early last year - with more expected to have done so this year.
Against this background schools are expected to improve their performance with a minimum of 40 per cent of pupils achieving five top A* to C grade passes including maths and English - compared with just 35 per cent last year.
Experts said that it would be the maths pass rate that would place schools in most difficulty of reaching the minimum target - partly as a result of a rise in the percentage of pupils taking the exam a year early to nearly one in four (23 per cent),
In English, too, experts believe it will be difficult to improve substantially on last year's pass rate when the grade boundaries were raised for those sitting the exam in June. The new boundaries have been fixed in line with the June figures - rather than the January ones which saw a flood of candidates achieving vital C grade passes.
Professor Alan Smithers, director of the Centre for Employment and Education at Buckingham University, said: “More schools are probably not going to make it because some schools relied on continually improving grades to carry them over the floor target.”
Ofqual has clamped down on that - insisting that the pass rate should be “broadly” in line with previous years as a result of its policy of “comparative outcomes” between different years.
If schools fail to reach the minimum floor target, they face inspectors from the education standards watchdog Ofsted being sent in - and the prospect of being forced to become an academy with a sponsor appointed to it by Education Secretary Michael Gove. In such cases, headteachers often face the sack.
At present, around 200 schools are below the Government's target for last year of 35 per cent of pupils reaching the required five A* to C grade passes including maths and English.