IT IS better known as Spiderwort, can grow 60cm tall and is native to the New World from southern Canada to northern Argentina.

But when students at Ysgol Friars in Bangor were instructed to use one of the leaves from the perennial plant Tradescantia in their A2 practical biology exam, they claimed it was virtually impossible to find locally.

Headteacher Neil Foden has now called on exam board OCR to discount the question, which was worth 16 marks out of 60 in the paper, rather than see it as a special consideration case, as his candidates were disadvantaged.

In a letter to the exam board he said it was the only fair thing to do, bearing in mind the difficulty his staff had in finding the leaves.

But OCR claims the plant can be found in most garden centres, and it is hugely popular throughout the UK. It confirms, however, that it did send out photographs of the leaf for students and staff who complained they could not get hold of one.

In his letter, Mr Foden said this was proof the choice had been unwise.

Speaking on behalf of other schools and students who had found the leaves - sometimes called purple hearts - difficult to locate, he said they were exchanging blogs about the unfairness of the question, which asks them to practically assess the leaf, taking into consideration its rarity.

He also said it was not the first time there had been a problem with the paper, saying pupils had become extremely stressed last year when an experiment with enzymes set by the board did not work out.

“My science staff have better things to do with their time than going out to look for leaves,” Mr Foden said in his letter.

“I am firmly of the view that this question should be discounted from the marking of the paper rather than pursuing special consideration. I would also welcome your comments on how the board intends to reassure schools that the setting and organisation of the paper is at least competent, bearing in mind this does not seem to be a one-off.”

Mr Foden claims his examination officer was told by OCR to submit a special consideration request for all candidates. But he said in the letter: “When we have been asked for special consideration in relation to staff absence, for example, OCR has told us that it is not appropriate for groups.

“How will the board be able to assess whether such large groups have been disadvantaged?”

A spokesperson for OCR said: “We are aware that some schools and colleges experienced problems with the A2 biology practical.

“A small number of schools and colleges found it difficult to generate the expected results and a few were unable to obtain the species of plant. OCR is putting in place procedures to allow for these difficulties. We apologise to students affected and assure them no candidate will be disadvantaged.”