A head teachers' union has expressed concern over this week's SATs exams for 10 and 11-year-olds amid claims that an a paper left some pupils "in tears" and damaged their "mental health and wellbeing".
Hundreds of parents and teachers have complained online about Wednesday's Year 6 reading exam, with one saying on Mumsnet that her daughter had found the paper "really hard and awful".
The National Association of Head Teachers, which represents heads at the majority of primary schools, said it plans to raise the issue with the exams team at schools regulator Ofqual.
Sarah Hannafin, the union's head of policy, said: "We are very concerned about reports from our members about the Sats reading paper.
"Members have told us that the choice of texts was not accessible for the wide range of experiences and backgrounds children have and the difficulty was beyond previous tests, leaving children upset, and with even staff struggling to understand the questions.
"We will definitely raise these concerns with the Standards and Testing Agency and also the Ofqual National Assessments team."
SATS, or Standard Assessment Tests, are used to measure children's English and maths skills in Year 2 and Year 6, and consist of six 45-minute papers.
The Department for Education (DfE) website says SATS are meant to "measure school performance and to make sure individual pupils have the support that they need as they move into secondary school".
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Kerry Forrester, a head teacher at a Cheshire primary school, has written to her local MP expressing concern about the "negative impact" of the exams on the "mental health and wellbeing" of her pupils.
In a letter she shared on Twitter, Ms Forrester says this year has seen "the most negative impact on our children that we have ever experienced".
"Tears flowed from our most capable readers and stress levels rose amongst all others," she said, adding that "this was the most challenging reading test I have seen in my 29 years as a teacher".
Beth Southern, an educational consultant and qualified primary school teacher from Bury, Greater Manchester, said her son was "disappointed" after this week's English paper turned out to be much more difficult than he had expected.
"My son feels disappointed that he found the reading test yesterday so challenging. He said the texts were long and wordy and that he had to use a lot of time trying to understand them, which didn't leave enough time for the questions," she said.
"He knows he was fortunate to finish when others have been left in tears.
"I have been told yesterday's test was dense, packed with difficult vocabulary, idiomatic language and a huge amount of inference was needed to complete it.
"It's awful that we assess a child's entire primary school reading ability on a single hour-long test that was way too complex for 10 to 11-year-olds to comprehend."
Jayne Robinson, 39, who works as a nurse, said many of her daughter's friends were unable to finish the exam, even though her Stoke-on-Trent school had been helping pupils prepare since Christmas.
"These exams have been much harder than the practice papers my daughter has sat," she told the PA news agency.
"My daughter had a lot of Sats practice but she said some of her friends couldn't finish the paper as it was too long. One of her friends made up answers at the end just to finish the paper."
A DfE spokesperson said: "Key Stage 2 assessments play a vital role in understanding pupils' progress and identifying those who may have fallen behind, so they can be provided with extra support if needed.
"Our test development process is extremely rigorous and includes reviews by a large number of education and inclusion experts and professionals including teachers, and we trial tests with hundreds of pupils over several years to ensure that all tests are appropriate.
"It's important that schools encourage pupils to do their best but preparing for these exams should not be at the expense of their wellbeing."
