Chief regulator Glenys Stacey says Ofqal has noticed a pattern in appeals of exam results from schools.
The analysis that we have done has shown that there is tactical appealing at critical grade boundaries - C/D at GCSE and B/A at A-level, that doesn't mean that every appeal at that boundary is tactical, but you can see from the pattern that it would suggest there is tactical appealing.
Secondly, the way the appeal system is designed at the moment, and indeed headteachers agree with us, that where you're within a couple of marks of such a grade boundary it's worth appealing because it is a one-way bet.
More top news
Ed Miliband will order an emergency recruitment drive of nurses so an extra 20,000 will be working in the NHS by 2020.
Sir John will give a speech later today saying a Labour-SNP government would be "weak and unstable" and wreck Britain's economic recovery.
Nigel Farage has told ITV News he would "happily" accept Christian refugees into Britain because they have "literally got nowhere to go".