Primary school teachers in England have taken to social media to vent their anger about what they claim are inconsistencies in the marking of this year's national curriculum test (Sats).
Using the hashtag #SATsshambles on Twitter, teachers have listed a range issues and are calling on all schools to go through their pupils' marked papers to check for errors.
The Department for Education said results of the tests were "robust and accurate" but head teachers could apply for a review of contested marks.
According to the teachers tweeting, 10- and 11-year-olds were asked to put punctuation in a pre-written sentence and - even though they got the right answer - did not get a mark because their commas were not curved the right way or their semi-colon was too large or not in precisely the right place.
They also complained about marking guidance which they claimed only markers, not teachers, had access to.
Primary head teacher Cathryn Throup tweeted some of the issued guidance which gave details of the "origin, height, depth and orientation" of semi-colons - or where pupils' should write their answers.
In particular it said:
- Neither element of the semi-colon should start higher than the letter 'l'
- The dot of the semi-colon must not be lower than the bottom of the letter 'w' in the word 'tomorrow'
- The orientation of the comma element of the semi-colon must be inclined to the left or straight down. It cannot incline to the right.
Primary teacher Liz Hindley, who tweets as @Leaping_liz, put up pictures of four answers all featuring the semi-colon in the correct place, but two were given a mark and two were not.
"The lack of consistency is so frustrating," she said.
Other teachers raised similar issues, such as pupils' answers straying outside of the box.
Brian Walton, head teacher of Brookside Academy in Somerset, told the BBC that schools had not been told that markers would mark pupils down for misshapen semi-colons and answers straying outside of a box.
"The markers had guidance that none of the teachers, none of the schools knew about, so a lot of this guidance about the size and the shape and the orientation and how we form letters - we didn't know that," he told the BBC's Victoria Derbyshire programme.
"Remember, they [pupils] are putting written semi-colons in text type with no gaps between the writing at the same time - we're really getting pernickety when we're getting to that level."
Mr Walton said he did know the scale of the problem, but had already had 50 or 60 heads in his area contact him with concerns.
Writer and poet Michael Rosen tweeted: "The punctuation police demand that the mark has to be drawn correctly and at the right angle."
'Robust and accurate'
In a statement, Pearson, the company which administered the Sats, 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."
A spokesman for the DfE said there were "a number of measures in place to ensure that schools' Key Stage 2 writing teacher assessment judgements are robust and accurate".
"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."
But teacher unions criticised the marking for being inconsistent, saying pupils were being marked down on a technicality when it was clear they knew the correct answer to the question.
Russell Hobby, general secretary of school leaders' union NAHT, said: "We now operate within a testing culture which appears focused on catching young children out rather than recording their achievements.
"Such a culture will swiftly erode the confidence of parents and teachers that the system is operating in the best interests of pupils.
"The stakes are so high that we seem unable to apply reasonable common sense."
Kevin Courtney, general secretary of the National Union of Teachers, said: ""We already know that moderation is inconsistent and open to gaming.
"Now, teachers are finding out that marking is unreliable too.
"The system does not deserve anyone's trust, and it should not be the basis on which schools are held to account."
Last week, official figures showed two-fifths (39%) of primary school pupils in England had failed to meet the expected standard in reading, writing and mathematics.
However, this summer's results were an improvement on the success rate last year (53%), which was the first year of new, more rigorous tests.