Teachers are to be given the right to appeal if their school is found guilty of cheating in national tests following complaints from heads that the current system is unfair and secretive.
The move, to be announced next week by the Qualifications and Curriculum Authority, comes as the regulator revealed that the number of schools investigated for cheating rose to a record 593 last year.
This was 41 per cent more than in 2003. However, only five schools' results were annulled, the lowest figure for at least four years. Some 1.8 million pupils will take the tests next month.
For the first time since the tests were introduced in 1991, the QCA is to publish its procedures for investigating malpractice allegations.
Schools under investigation will be sent reports before the investigations are completed and will be given the chance to represent themselves at QCA hearings. The rule changes come after a campaign by Essex heads, backed by the National Association of Head Teachers, who highlighted a string of problems with the investigations system, which some labelled "Kafkaesque".
The Essex Primary Heads' Association took up the case of Diane Stygal, head of Waltham Holy Cross junior, in Waltham Abbey, one of England's top schools in the league tables before its results were annulled by the QCA last year.
Mrs Stygal said she had been "condemned by a kangaroo court" after being investigated for alleged irregularities in key stage 2 tests. The QCA said pupils had not completed papers unaided but Mrs Stygal denied this and her governing body backed her and took no disciplinary action.
Even after she was told of the decision to annul the results, which put her school bottom of national league tables, Mrs Stygal said she was not told the precise nature of the case against her school.
There was no opportunity to appeal against the regulator's judgement.
The QCA, which can investigate after malpractice allegations, can annul results. Previously no rules were published for its investigations, and governing bodies then had to decide whether to take disciplinary action.
Staff are given full details of the case against their school only if disciplinary action is taken, leaving, it is claimed, an unexplained stain on a school's reputation if results are annulled.
The changes introduce detailed reports for schools but heads are unlikely to be given full details of charges in the early stages of investigations.
The QCA is still not revealing the criteria by which its maladministration committee decides whether to annul a school's results.
David Hart, NAHT general secretary, said it was astonishing that the QCA had previously not published clear rules to tell heads what happened if they found themselves at the centre of allegations.
He said: "Until now, the QCA was able to declare a school's results null and void, without any right of appeal by the head. Justice could not be seen to be done, because the procedures and the powers of the QCA in these cases have almost been a state secret. I therefore welcome the QCA's decision."
Ruth Brock, executive chair of the Essex Primary Heads' Association, said:
"The QCA has done what we knew they needed to do, but they haven't gone far enough to ensure that schools don't suffer when the case against them has not been proved beyond reasonable doubt."