Pupils should be discouraged from taking GCSEs early because it is often harmful, Michael Gove said yesterday.
The Education Secretary has written to Ofsted chief inspector Sir Michael Wilshaw, asking him to investigate.
In the letter Mr Gove says that taking a GCSE early can be beneficial where it is part of a planned programme. But he adds this has become "a damaging trend".
In 2010, 29 per cent of those entering early got at least a B in their maths GCSE, compared with 37 per cent of all entrants. And 30 per cent of early entrants got at least a B in English, compared to 41 per cent of all entrants.