Thousands of pupils are missing out on As and A* grades at GCSE because more schools are choosing to enter children early for English and maths exams, the education watchdog has warned.

Ofsted said it will be "critical" of the choice to enter pupils early if schools are not "absolutely confident" that they will achieve top grades.

The watchdog's chief inspector Sir Michael Wilshaw said: "We think early entry hurts the chances of the most able children getting the top grades of A*, A and B, which they need to progress to A level and certainly to university."

Statistics have shown a growing trend for early entries for GCSE maths and English examinations since 2006, with a third of all pupils taking these early.

But Ofsted figures suggest that this practice may be hindering pupils from reaching their full potential. Children who were high achievers in primary school were less likely to achieve A grades if they took these exams earlier than high primary school achievers who were not entered early.

Copyright Press Association 2012