More concerns have been raised about the marking of this year's Sats, with teachers taking to Twitter over the weekend to share examples of questions which they felt were incorrectly marked.
Using the hashtag #Satsshambles teachers pointed out multiple examples of questions which they thought were wrongly scored.
Teachers speculated about what could account for some of the errors.
According to a commenter on Tes Community, markers have had significantly more marking to do this year. They said that last year they marked nearly 19,000, but this year it's been over 28,000.
However Pearson, which is responsible for the Sats marking, said that markers had the same size allocation or marking as in previous years. The company also said that all marking had been done by humans, and not optical readers.
A Pearson spokeswoman said: "Marking quality is extremely important and is something we monitor continuously. In the unusual circumstance that there is an error, there is a review process in place which ensures a fair and transparent system and enables Pearson to correct any discrepancies and ensure pupils receive a fair mark."
Brian Walton, headteacher of Brookside Academy in Street, Somerset who tweets @Oldprimaryhead1, has been encouraging schools to tweet examples of marking errors and said by this morning he had had 4,845 Twitter notifications.
Mr Walton said the marking issue "could be on an unprecedented scale".
The general secretary of the NUT teaching union, Kevin Courtney, has asked teachers to flag up examples of the errors.
The new evidence of errors comes after teachers expressed outrage on Friday over pupils whose correct answer has been marked wrong by examiners in the spelling, punctuation and grammar Sats test.
Some children who accurately positioned a semicolon in a sentence have had their answer marked wrong, while others have been told their answer is correct.
A Department for Education spokesman said: “There are a number of measures in place to ensure that schools’ key stage 2 writing teacher assessment judgements are robust and accurate. Headteachers have a statutory duty to ensure that their school’s judgments are an accurate assessment of pupils’ attainment. They are also encouraged to moderate their judgements with other schools.
“The Standards and Testing Agency takes any issues with the accuracy of schools’ teacher assessment judgments very seriously. Any concerns about particular schools should be reported to the STA so that they may be properly investigated.”