“Shocking” marking errors in this year’s national tests have led to pupils being given the wrong levels, according to primary headteachers.

They told TES that their results, published last week, contained more marking mistakes than in previous years. The errors included cases where correct answers were awarded no marks.

One headteacher fears that if the inaccuracies are not overturned, they could cause his school’s Ofsted rating to fall.

The NAHT headteachers’ union is so concerned that, for the first time in years, it has issued instructions to its members to check results in detail and submit any evidence of mistakes.

The fears come after revelations, published in TES last month, that Sats markers believed the launch of a fully online marking system had introduced errors to the process (“Pupils could be given `wrong’ marks for Sats”, News, 12 June).

`Furious is an understatement’

Clem Coady, headteacher of Stoneraise Primary in Carlisle, said that at least three of his school’s 11 Year 6 pupils had been awarded the wrong level in English tests because of marking mistakes.

“We were shocked when there were correct spellings marked wrong,” he said. “To say we were furious is an understatement.The kids work exceptionally hard and for them not to get the credit they deserve is shocking.”

TES has seen examples of six correctly answered questions that were awarded no marks (two are pictured, left).

Amanda Hulme, headteacher of Claypool Primary School in Bolton, told TES that marking mistakes had been made in the maths papers of 12 of her 30 Year 6 pupils. Two of these errors affected the child’s overall level, she added, and the papers would be sent for re-marking. “Every year we go through the papers that are close to the [grade] threshold and we rarely have to send a paper back,” she said. “This is really unusual.”

One Claypool pupil who wrote the numbers 1 and 7 in a similar way answered a question correctly but was awarded no marks. Last month, a marker told TES that the online system used by test administrator Pearson did not allow markers to see a child’s full script. This meant they had no context in which to understand a child’s handwriting, the whistleblower warned.

Graham Frost, headteacher of Robert Ferguson Primary in Carlisle, said his school was planning to contest the results of four of its 35 Year 6 pupils. “For the school, there is so much hanging on these tests,” he said. “In my view, every incorrectly marked test is a scandal.”

Another school leader, who asked not to be named, was concerned that the results could bring down his school’s Ofsted rating from “good” to “requires improvement”. “With a small cohort, a small number of bad results can drop your overall results through the floor,” he said.

NAHT general secretary Russell Hobby said: “We’re more worried this year than in previous years. In any new system, even if it’s well-designed, there will be mistakes.”

A Pearson spokesperson said: “We would like to reiterate to students, teachers and schools that they can be confident that exam papers are marked at the highest standards at all times.

“If schools want to apply for a review there is a clear process to do this, and if an issue is identified we can correct it quickly.”