The government has been forced to issue clarification on whether pupils can bring rulers into the tests, after a series of contradictory statements about whether they could be used.

Teachers expressed confusion after the sample test for 2016 said rulers would be banned, but Catharine Parkes, of the Standards and Testing Agency, later said that a ruler was the only mathematical equipment children were allowed.

After enquiries from the TES, a spokesman for the Department for Education confirmed that “children are allowed to use rulers with numbers on them”.

A number of teachers had said on Twitter that the varying advice was creating confusion.

Prior to the government’s clarification, Michael Tidd, deputy head of Edgewood Primary, Hucknall, Nottinghamshire, told TES: “It has been frustrating throughout the last year to be constantly waiting for updates and then finding new information that contradicts the old. Recently we were told by ministers that it was “disingenuous” to suggest that it was because the department didn’t know what it was doing.

“Yet here we are again, with contradictory information being published such that teachers are left trying to guess what is and isn’t permitted. The department needs to remember that teachers can find themselves in stiff trouble if they make errors on such matters, yet confusion abounds.

“Combined with the ongoing delays to reading exemplification, the changes to writing moderation, the late changes to dates, the inaccuracies of the Assessment and Reporting Arrangements statutory guidance, it leaves teachers confused and frustrated and children poorly served. The department should be embarrassed and apologetic.”

It comes after the rules on marking exclamation marks in the grammar, punctuation and spelling test for seven-year-olds were interpreted as ministers wanting to restrict their use ─ something Nick Gibb, schools minister said had been misunderstood.

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