Headteachers could “explore all options for action” if they find that assessment and accountability “continues to be harmful to the health and education of our children”.
The call came as the NAHT union raised concerns that test and exam results can be manipulated by politicians to suit their own agenda.
Delegates at the union’s annual conference in Telford this afternoon debated a motion calling on its executive to “expose and discredit the statistical and politically-motivated manipulation of test and grade boundaries” and highlight the “harmful and unjust implications” this can have of students and teachers.
The motion was amended to add: “If national executive identified compelling evidence that government policy on assessment and accountability continues to be harmful to the health and education of our children, conference calls on national executive to explore all options for action.”
Speaking after the motion was passed, Russell Hobby, general secretary of the union, said: “It is important that, in negotiations with government, NAHT is able to explore all options.
“We know from this time last year that it is helpful to have all options on the table in order to deliver the changes schools need.
“NAHT always prefer constructive dialogue to confrontation, but it is important that NAHT’s executive is empowered to act in the best interests of its members using all possible means.”
Delegates also approved a motion calling for the union to lobby for national sampling for all tests at key stage 2, rather than compulsory testing of the whole cohort.
Speaking ahead of the resolution, Graham Frost, a headteacher from Carlisle who proposed the lead motion, said: “We want to remove any possibility of government agencies manipulating school performance data to support a particular political agenda.”
He said that his own research shows a steady rise in primary school SATs results over time, but small irregularities appearing around the time of general elections.
“What I’m contending is that I suspect there is a tendency to be tougher or less tougher in where they set those grade boundaries depending on the agenda,” he said.
Fellow Carlisle headteacher Clem Coady said there are concerns that boundaries are changed to suit a particularly narrative.
“You see the boundaries changing year on year depending on what stories they want to do.”
The motion was supported by 99 per cent of delegates.
Last month, education secretary Justine Greening announced a consultation on primary assessment, saying at the time that she recognised the need for a “settled system”, which supports teachers, allows schools to benchmark their own performance and holds schools to account in a “fair and accurate” way.
