NAHT union on GCSEs: 'You can't change the goalposts'
25 August 2012 Last updated at 13:22 BST
The National Association of Headteachers has criticised grade changes to English GCSEs which one think-tank says could have affected 10,000 pupils.
The union is demanding that Education Secretary Michael Gove sets up an independent inquiry into the changes but the regulator Ofqual says it believes this year's GCSE grades are correct.
Kathy James, Director of Policy and Campaigns at NAHT, said the marking reforms put in place part-way through the year amounted to "changing the goalposts", and that it put pupils who sat the exam later at a disadvantage.