A “rogue marker” leaked a test the day before it was taken on Tuesday by children aged 10 and 11 in England, the Department for Education has said.
The Sats answers had been mistakenly published on Monday on a password-protected website for test markers, schools minister Nick Gibb told MPs.
He said an individual then tried to leak them to a journalist but it appeared they had not become public.
The DfE blamed an “active campaign” to “undermine these tests”.
The test was valid and had gone ahead as planned, Mr Gibb told MPs in response to an urgent question on the matter.
He said the spelling, punctuation and grammar (SPAG) test had been “mistakenly uploaded” by the test supplier, Pearson, onto a secure website, and that an individual with access to the site had then leaked the test to the media.
Mr Gibb said it was a “serious breach” but that “teachers and parents should have confidence in the test.”
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