Labour could meet an early test of union opposition if it does not indicate by June that it is willing to enter into talks with teachers and councils on Higher Still.

A motion from Peter Wright, West Lothian, committing the association to ballot its 6,800 members on a boycott of the reform was approved with just one abstention. It calls on the Secretary of State to delay the changes pending these “meaningful discussions”.

While some delegates were concerned about issuing threats and demanding action from a new Government within two months, the overwhelming mood was in favour of sending a signal. It was “the only way of underlining our determination”, Mr Wright said Bill Fitzpatrick, East Ayrshire, declared: “If we are going to start on Higher Still next year, I am going to have to skim this year’s requisition which must be sent into the school office in 20 days’ time.

“It is getting to the point of no return and we say clearly to the politicians that, if they break their promise to provide us with the means to implement Higher Still, they should not expect us to co-operate with it.”