The number of pupils sitting multiple exams in the same subject has raised major concerns among educationalists ahead of today's release of GCSE exam results.

Exam regulator Ofqual said pupils entering for more than one qualification in the same subject, particularly in maths, was one reason why this year's exam results could look different to last year.

Advisory Committee on Mathematics Education (ACME) committee member Richard Browne said: 'A target-driven culture based on league tables has skewed behaviour in schools and encouraged multiple entry.

'The practice of early entry has a negative effect on most students' mathematical education and hinders their progression to a wide range of subjects post-16 and in higher education. Repeated resitting and multiple entry reduces the time spent developing students' mathematics skills and knowledge, as well as having significant extra cost for schools.'

A Department for Education spokesman said they were 'increasingly concerned' about early and multiple entry and that evidence had shown that entering exams early, re-sitting, or taking another exam in the same subject, is not good for pupils.

'The changes we have made to GCSEs – including moving to end-of-course exams – and reforms to the accountability system will help address this,' she said.