Almost 500 students were entered for maths GCSE with more than one exam board this summer, according to Ofqual.
Allowing students to sit the same subject with more than one board gives them two attempts at the same exam and is potentially seen as malpractice.
It is believed it may be happening owing to the pressure that schools are under to achieve high pass rates.
Freedom of information requests to Ofqual by Tes reveal that 499 pupils were entered for maths GCSE with more than one exam board in summer 2017, and 31 schools entered students with two exam boards.
It comes after the Joint Council for Qualifications (JCQ) confirmed last month that 15 schools were being investigated for potential malpractice after double entering pupils for maths GCSE in 2016.
Maths teacher Mel Muldowney, who blogs as Just Maths, has also been investigating the practice – and says she is angry and concerned about the effect on pupils.
She said: "It is happening. It may be the pressure of accountability, which is massive, and sometimes they are doing it for the kids – because that kid needs a grade 4.
“But it makes me really sad because those kids are sitting nine hours of maths exams. It can't be a great experience for them."
She added: "It has been a tough three years for maths teachers with the new GCSE, and the vast majority of schools have played by the rules. We have worked our asses off to get better results. It is about being fair to everybody."
While double entry in itself is not malpractice, schools may not alter the GCSE timetable to enable students to be entered for more than one exam in the same subject. As the GCSE maths exams are timetabled to take place at the same time, double entry is, in effect, malpractice.
For maths GCSE, there are different boards, as well as two tiers of papers: foundation and higher. The foundation tier paper has a top mark of grade 5. The higher tier paper is designed to test pupils working between grades 9 and 4 (with a ‘safety net’ grade 3 for students scoring a small number of marks below grade 4.)
Ofqual’s breakdown of the double entries revealed that the greatest number of pupils, 278, were entered in two foundation papers. There were also 217 pupils who were entered for a foundation paper and a higher paper, and four were entered for two higher papers.
Number of students entered for each combination of board and tier
Source: Ofqual. Response to FoI
This year was the first year of the reformed maths GCSE. The majority of students who were double entered (61 per cent) took two legacy qualifications. The legacy qualification is the old A-G grade maths GCSE which has now been superseded but could be taken as a resit for the final time this summer.
More than a third of those who were double entered, 36 per cent, took two reformed qualifications, with just 3 per cent of students taking a combination of legacy and reformed qualifications.
Only 10 centres had double-entered more than 10 students – but one of those had entered more than 200, or 41 per cent of the total number. Cases where pupils were entered but did not sit the assessment were excluded from the number.
The exam bodies are responsible for sanctioning centres that are guilty of malpractice. Sanctions can range from a written warning to withdrawing recognition – meaning the centre can no longer offer that exam body’s qualifications.
If malpractice was found in such a case, the sanction is against the centre and a candidate's result would still stand.
A JCQ spokesperson said: “Exam boards take all allegations of malpractice seriously and are committed to delivering a fair and robust system.
"As we have stated previously, where there are allegations of malpractice the JCQ Centre Inspection Service will look at every case and investigate if necessary. It is important to note when looking at the data that making a double entry is not in itself malpractice, changing the timetable to accommodate double entry is.”