Edexcel has replaced the A-level paper for further maths that pupils are due to sit this week after concerns were raised of a second exam leak.
The board discovered that a packet containing the paper was opened at the school or college that is at the centre of a police investigation into last week's maths paper leak.
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In a statement, Pearson – the company that runs Edexcel – said: "As part of Pearson’s ongoing investigation of a centre into the breach of the A-level maths paper 3 on statistics and mechanics last week, and due to the actions of this centre, we have taken a decision to replace the forthcoming further maths A-level paper scheduled for this Thursday 20 June.
"The investigation of the centre revealed that a packet containing the further maths paper, which will be sat by c.7,000 students, had been opened by an individual at the centre.
"While we have no current evidence to suggest that the paper or any of its questions have been shared, we are taking the necessary precautionary steps to safeguard the exam for the students sitting it.
"We are making arrangements to deliver the papers to all centres shortly before the exam, apart from the centre that is the focus of our investigation, where we are making separate arrangements to ensure these students can complete their exams."
Schools with entries for the qualification will be contacted by Pearson today.
Sharon Hague, senior vice-president of schools at Pearson, said: “We have reached out to all of our centres directly to inform them of this decision.
"We will continue to support and communicate with them through this unusual yet necessary step, that is vital for the safeguarding of confidence in the examination system and to ensure fairness for all learners.
“Our message to students is not to worry about this and focus on your revision as you normally would.”