The Department for Education has scrapped a spelling test which was set to be taken by hundreds of thousands of seven-year-olds, after it was accidently published online.
The test, which was supposed to be taken in May, was part of a Key Stage 1 Sats assessment.
But it was accidentally uploaded in January onto the Standards and Testing Agency (STA) website as a practice, where it was seen by some students.
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The mistake was spotted by a teacher at one of the schools carrying out a trial of the test, and Russell Hobby, leader of the National Association of Head Teachers head said teachers had "no way of knowing how extensively it has been used by schools and parents".
STA chief executive Jennifer Coupland attributed the incident to human error and "a failure to follow appropriate clearance processes".
She added: "An immediate review is under way to establish the precise facts and we would like to apologise to schools and parents for any distress caused."
In a statement, schools minister Nick Gibb confirmed that the DfE was withdrawing the test.
He said: "We have worked swiftly to find a solution to the administration of this year’s KS1 grammar, punctuation and spelling tests.
"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.
"Schools will still need to submit a teacher assessment judgement based on pupils’ work in the classroom as has always been the case."