A Tunbridge Wells school has lodged an official complaint with an exam board after crucial papers were left out of test bundles.

Tunbridge Wells Girls' Grammar School head teacher Linda Wybar wrote to parents informing them OCR — the exam board behind the Southfield Road school's A2 Biology exam — had failed to provide a formula sheet for standard deviation.

A spokesman from OCR said: "For one question on OCR’s A Level Biology paper H420/01 (Question 20a, worth 3 marks out of a total of 100), the formula for standard deviation was not provided.

"Some of OCR’s guidance to schools and teachers about the syllabus indicated that candidates would be provided with this. OCR apologises and will address any impact of this during marking and grading.”

It is the third time OCR has been forced to apologise this month.

Last month an error in a lead characters' family background made its way into the board's GCSE English Literature paper, while last week Psychology students were forced to unpick a confusing A Level question.