A head teacher has hit out at an exam board which sent out papers that were "impossible to do" and contained previous exam extracts.

David Craggs, of Gad's Hill School in Higham, said it beggared belief that AQA could have sent out the maths paper to thousands of pupils with errors in it.

AQA has now apologised after GCSE students across Kent were given questions from an old paper this morning.

The board has blamed a printing error, after pupils throughout the county and beyond were given wrong papers.

It said "some" of the 31,000 maths pupils sitting the test were given questions previously used in March.

It follows a string of errors in A-level and GCSE papers this summer, including impossible questions.

Earlier this month the exam regulator Ofqual said mistakes in AQA papers were "disappointing" and "unacceptable".

But Mr Craggs (pictured left) dismissed the blunder as a "schoolboy error".

He added: "It's incredible.

"We are all human and we all make mistakes - providing it happens occasionally.

"But this exam season we have had almost daily stories with exams boards making blunders such as this - with questions that are impossible to answer and similar cases such as we have today.

"It beggars belief!"

He said the mistake was spotted when a colleague alerted him to errors in the paper. A sea of pupils' hands then went up, and an urgent call was put in to AQA.

It's believed Gad's Hill was among the first in the country to spot the blunder - with sections of the paper coming from a previous exam, "impossible" questions and no question two.

Audio: Gad's Hill head teacher David Craggs, on hearing of the exam blunder

Mr Craggs added: "If the exam board were forced to do an exam in running an examination system they are probably heading for a D grade!"

Year 10 pupils at Dover College were also handed the wrong paper.

Headmaster Stephen Jones said: "It's a great sadness for the pupils as it makes their lives much harder both in the exam because one of the questions was simply impossible and also it makes their concern over the award much greater."

He said there were always errors, but this one would have been "a very easy one to check and find out."

A full statement from AQA said: "We are aware there has been a problem with the printing of our GCSE Maths Unit 2 Foundation exam paper and are very sorry that this has caused some students distress this morning.

"[the exam boards] have managed to make an almost schoolboy error...” – head teacher david craggs

"From the information we have at this stage, it seems that some of the papers contained questions from the March 2011 paper.

"We understand the problem version of the paper begins and ends with June questions, but has March questions in the middle of it.

"The error appears to be limited in that we understand some schools have correctly printed papers, some have the problem version of the paper and others have a combination of both."

Altogether, there are 567 schools and colleges, with 31,659 students taking the paper.

The statement said schools were told that students should attempt the paper as it was.

The board would then consider what action to take when AQA understood the extent of the problem.

It continued: "The batches of papers that we checked as part of our quality assurance process are all fine and we are in the process of investigating with our printers how this problem has arisen.

"As with any problem of this nature, our top priority is to protect the interests of students and we will ensure that no student is disadvantaged by this printing error."