A national spelling test for Year 2 pupils has been cancelled by the Schools Minister after a teacher spotted it had mistakenly been published online as a practise paper.
Charlotte Smiles was teaching at a school that was officially trialling the final exam ahead of the national roll, when she realised one child had already seen the test paper.
Approximately half a million children were due to take the Key Stage 1 spelling and grammar test in May, as part of their SATs.
Nick Gibb, Schools Minister, said: "To remove any uncertainty and clarify the situation for schools, I have decided that we will remove the requirement on them to administer the Key Stage 1 grammar, punctuation and spelling test for this year only."
Smiles said she was alerted to the fact some children had already seen the paper, when a boy in her class said he "knew the answers" and appeared to know what was coming next.
When she checked the Department of Education's (DoE) website she found the paper had published as a sample.
"It's actually been there since January 26," she told the BBC.
Gibb explained the steps that were taken when the DoE was "informed of the breach".
"I ordered the Standards and Testing Agency [STA] to undertake an investigation into how this breach occurred," he said.
"I have also commissioned a root and branch inquiry into the operations of the STA.
"In the meantime we have worked swiftly to find a solution to the administration of this year’s KS1 grammar, punctuation and spelling tests.
"Schools will still need to submit a teacher assessment judgement based on pupils’ work in the classroom as has always been the case.
"However there will be no requirement this year for them to administer the KS1 grammar, punctuation and spelling test or use the result as part of that assessment.
"Our immediate inquiry has shown none of the other KS1 test papers have been affected by this error.
"This is a clearly regrettable incident and I am sorry for any concern it has caused teachers, parents or pupils."
Jennifer Coupland, Chief Executive of the Standards and Testing Agency, said: "We were made aware on 20 April that sample guidance material published by the STA, to be used with the modified version of the Key Stage 1 spelling test, contained the live test words rather than the sample test words.
"As soon as we were made aware, we removed the document from the website.
"We believe this issue has arisen as a result of human error by a member of staff within the Agency and a failure to follow appropriate clearance processes.
"An immediate review is underway to establish the precise facts and we would like to apologise to schools and parents for any distress caused."
Pupils in this year group take six test papers for their SATs: two papers on English grammar, punctuation and spelling; two papers on English reading and two papers on mathematics.