Exam boards have been told by Ofqual that they have “lessons to learn” after an investigation into allegations of exam cheating at a London secondary took nearly two years to complete.

Staff at Kingsdale Foundation School allowed students to make second attempts at coursework after their original work had been marked by teachers, and allowed “unauthorised emergency scribes” to be used by exam candidates who were capable of writing, according to reports finally made public on Thursday.

They reveal that one board, OCR, discarded all GCSE science coursework marks from the school, having “lost confidence” in their “validity and reliability”, while another board, AQA found inconsistent and overly generous marking in some GCSE English coursework.

The school claims the reports, written by the boards, contain “misleading and inaccurate” statements. Ofqual has noted that the “the reports have not been agreed by the school” but has decided it is in the public interest to publish them.

The OCR report shows that a member of school staff received a written warning from the boards for giving students “more assistance than is permitted”.  

The allegations, involving four exam boards, were first made in July 2011, the same year that Prime Minister David Cameron described the secondary in Dulwich, South London, as “brilliant”.

The boards initially allowed the school’s chair of governors to appoint an “independent” investigator to lead the inquiry. The investigator had previously advised the school, a fact the school says the boards were fully aware of before approving the appointment.

But Ofqual has now told the boards that in future it expects them to: “Delegate investigation to the school or governing body only when the exam board has confidence that the investigation will be prompt, thorough, independent and effective.”

It took until May this year for the boards’ investigation to conclude. They initially refused to publish the results, saying that they remained confidential.

Ofqual overruled that decision on Thursday, acknowledging the boards had taken “a long time” to complete the investigation.

One of the reports says that some BTECs in applied science at Kingsdale were not awarded by the Edexcel exam board because the portfolios “were not at a standard to allow certification”.

But Kingsdale said it “had not yet completed its own internal moderation process and had therefore not sought certification for these BTECs in applied science”.

AQA looked at GCSE English and English literature coursework and found “irregularities”, including “discrepancies between marks”, some assessment “much higher than it should have been” and annotation that was lacking or inconsistent.

The WJEC board found there had been “unauthorised use of scribes” because three students had handwriting that varied between exam scripts in different subjects. It also found that candidates may have been invigilated by their subject teachers. Despite the boards’ findings, only one written warning was issued.

TES revealed in July 2012 that one of the reasons for the delay in the investigation was that the school had considered taking legal action against the exam boards.

Whistleblowers who made the original allegation said then that they had “lost all faith” in the investigation.

But Kingsdale headteacher, Steve Morrison, said the inquiry was delayed because the exam boards were trying to “put their houses in order” and the school had wanted to bring it to a quicker end.

“We have expressed our concerns to both Ofqual and the examination bodies over what we consider to be misleading and/or inaccurate statements contained within them, particularly with respect to the report from OCR,” Mr Morrison said. “We are confident that outcomes compare favourably to many other enquiries over the same period in spite of the extended forensic examination of the school.

“The outcomes of investigations have produced no evidence at all of institutional or systemic malpractice or maladministration at the school. Parents, students and the public can have confidence in the integrity of past, current and future examination grades awarded at the school.”