England's exams watchdog is to "scrutinise" this summer's controversial International Baccalaureate grading, Tes can reveal.
Ofqual has requested information from the IB so that it can ensure that its results are in line with its rules.
Since IB results were released on Monday, nearly 10,000 people have signed a Change.org petition calling for "justice" for students, while one head has written to education secretary Gavin Williamson to highlight issues he has with the 2020 grading process.
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Some students have dropped up to 12 marks out of a possible 45 in the Diploma programme, achieving far lower scores than they had been predicted.
Ofqual revealed its decision to look into the grading process this evening following an inquiry from Tes.
"We have requested information from IBO to scrutinise the awards it has made this summer and satisfy ourselves that results have been delivered in line with our extraordinary regulatory framework," a spokesman for the regulator said.
This followed a response to Tes in the afternoon when Ofqual made no mention of plans to investigate.
This summer has already seen a "request" from Ofqual prompt a U-turn by the IB. After talks with the regulator it agreed that students in its Middle Years Programme students would now receive grades in core subjects after all, awarded on a similar basis to pupils studying GCSEs.
Today's earlier Ofqual statement, after Tes asked if there would be investigation, only said: “We are aware of the media coverage of IBO results following their release earlier this week.
"In May we published details of our extraordinary regulatory framework for vocational, technical and other general qualifications.
"Each awarding organisation has been responsible for developing its own model for issuing results in line with the framework, taking account of the purpose of its qualifications and the evidence and available data.
"If schools, colleges or individual students are concerned that an error has been made in the results issued by IBO, then they should follow IBO’s appeals process in the first instance.”
The IB says it understands there have been "mixed emotions" regarding the outcomes this year, and that it used students' coursework, school predicted grades and historic assessment data to calculate grades for this year.
A spokesperson said: "Prior to the attribution of final grades, this process was subjected to rigorous testing by educational statistical specialists to ensure our methods were robust. It was also checked against the last five years’ sets of results data, to ensure that it would provide reliable and valid grades for students."
The IB said the stability of its results had been maintained for this exam series and that it was confident it had awarded grades in the "fairest and most robust way possible" this year.