An investigation by exam boards into accusations of cheating at an "outstanding" secondary remains unresolved after more than 10 months because the school has threatened legal action over alleged problems with the inquiry, TES has learned.
Kingsdale Foundation School is entering its third exam season since the claims, described as "very serious" by the government, were first made last summer.
An independent inspector appointed by exams regulator Ofqual is overseeing exams this term at the school in Dulwich, South London. But whistleblowers who made the cheating allegations say they have "lost all faith" in the investigation.
They are concerned that the school is still using the same exams officer as when the allegations were made, a claim that Kingsdale has not denied. The school, described by Prime Minister David Cameron in May last year as "brilliant", faces accusations that pupils were allowed to make corrections after exams had finished and that grades were awarded for coursework that pupils did not do.
One whistleblower, still working at the school, said: "It is disgraceful that the report has not been submitted and a school can use taxpayers' money at a time like this by threatening legal action against a proper investigation."
A letter, seen by TES, written by Ofqual's chief regulator Glenys Stacey to the MP of one of the whistleblowers, refers to "legal action taken by the school against the awarding organisations". "This aspect has delayed the conclusion of the investigation," Ms Stacey writes.
When he was approached by TES, Kingsdale head Steve Morrison denied that the school had taken legal action. A statement from the school later revealed that legal proceedings have been considered, although "not yet commenced", to give the exam boards "the chance to rectify the position".
It is understood that the "legal action" mentioned in the Ofqual letter is a reference to a discussion between Kingsdale's lawyers and the exam boards.
Another whistleblower said: "I have lost all faith in the education system and those that oversee it. There is no longer anywhere for us to turn."
A third teacher said: "I think it's disgusting that brave members of staff put their necks on the line to tell the truth and yet it's been nearly a whole year since the investigation started and we are none the wiser to the outcome. The only difference is that the exams officer is now being `monitored' by the exam boards directly."
Ms Stacey's letter says: "A desire to bring the case to a close quickly cannot be at the expense of getting it right."
The letter reveals that the investigation is being run by four exam boards: OCR, Edexcel, AQA and WJEC. Ms Stacey says a "set of measures" were put in place "to ensure the safe delivery" of exams at the school in November and January, and will remain there this summer.
Last summer, when the allegations emerged, Mr Morrison said he was confident that Kingsdale, rated "outstanding" by Ofsted, would be exonerated, adding: "It is impressive the way the exam boards are dealing with this."
But in a statement made this week, the school said: "Over five months after the investigation started, Kingsdale Foundation School, on legal advice, expressed serious concerns about the investigatory process being followed by the awarding bodies and has asked for reassurances that the situation is rectified and the investigation is concluded.
"Legal proceedings have been considered but have deliberately not yet been commenced so as to give the awarding bodies the chance to rectify the position and bring the matter to a conclusion as soon as possible."