SCHOOLS should prepare for a “crucial election for education,” the leader of the National Union of Teachers said yesterday.

Closing the union’s last conference before it merges with the ATL in Cardiff yesterday, Kevin Courtney warned that new grammar schools were likely to be central to the Tories’ manifesto.

Mr Courtney, who had previously warned that the government was likely to expand selection via the back door, said the Prime Minister’s announcement yesterday of an early poll was “a challenge that our union will rise to.”

He said: “We believe that Theresa May has been very nervous of using a legislative route. She has no electoral mandate but she is now seeking one.

“So this debate is now very public. We have to popularise these arguments quickly.

“There are many who know that it was Margaret Thatcher who transformed most grammar schools and secondary moderns into comprehensives — and that she did that because middle-class families were crying out that their children weren’t getting in to grammars.”

Mr Courtney said the union would “scrutinise all party manifestos and report them to our members.”

The union will also use the election to push its opposition to primary-school Sats tests.

“We should be clear: teachers aren’t opposed to testing or assessing children,” Mr Courtney said.

“Teachers invented tests.

“But we want tests with a purpose: tests and assessments to give teachers real information that help children learn, tests to mark children’s real achievements and give them a sense of satisfaction.”

Yesterday morning the conference voted down a motion that proposed to “suspend arrangements” for this year’s Sats.

The defeated motion called for all “summative testing” to be boycotted.

East London delegate Sasha Elliott said the call would amount to a “waste of a precious ballot” and that the motion was “too vague to be credible union policy.”

But the union had already endorsed a motion calling for a boycott of Sats next year.

“Sats are the head of the monster,” executive member Jess Edwards said.

“Lets decapitate it and get rid of all testing in primary schools.”

Last week the Association of Teachers and Lecturers, which will merge with the NUT in September to create the National Education Union, voted in favour of a possible boycott of Sats.

The unions are likely to seek the support of the National Association of Head Teachers.