Delegates at the National Union of Teachers conference in Harrogate agreed to a commitment to encourage schools not to sign up to the pilot of the scheme from September and to ballot members for a boycott of the tests before September 2016, when they will be brought in for all schools in England.
Campaigners will be writing to all head teachers in England to urge them not to take part in the pilot.
Schools that intend to take part in the pilot year have to choose one of six providers of the baseline assessment before the end of this month.
Sara Tomlinson, a primary teacher and chair of Lambeth NUT who proposed the motion, said the vote was ‘unanimously’ passed.
Ms Tomlinson said, ‘We were totally buoyed up. We want to build on the momentum. Parents are our biggest allies here.’
‘We will be also writing to all heads to persuade them not to sign up to the pilot.’
The next steps will be to tell parents how they can opt out of the tests and talking to teachers about how they can object if their schools take part in the pilot.
The motion, which was the opening debate at the union’s annual conference over Easter, was passed unanimously with one amendment, to agree to have a ballot of members on the boycott before September 2016, when the baseline will be introduced in all schools in England.
Although the baseline is not statutory it will be used by Ofsted to measure schools’ performance, meaning that few schools are likely to opt out.
A public meeting will take place next month.
In her address, NUT president Philipa Harvey said that it was a ‘crime’ to test four-year-olds.
‘In their first few weeks at school, when children and their teachers need to be fostering a love of school and learning, and developing the relationships and conditions for this to happen, teachers will be testing children,' she said. 'Teachers are being driven by a testing agenda imposed on them instead of them being trusted to respond to the learning needs of the individual children that they are teaching and no doubt assessing.
‘This is going too far. It is up to us to make sure that we are telling everyone that this is outrageous. The more people who know the problems that standardised testing inflict on our children the more will speak out against it.’
The NUT’s boycott follows growing opposition to the baseline from many in the early years sector.
Last week, an open letter published in The Guardian was signed by a number of academics and educationalists, as well as children’s writers Michael Rosen and Philip Pullman.
Dr Richard House, educational campaigner and founder of Early Childhood Action, said, ‘This latest move by the NUT against baseline assessment simply confirms the feeling right across the early years field that these standard assessments of four-year-olds just have to be stopped.
‘The only reason why politicians see the need to test children at four (which is even before the compulsory school starting age!) is because England has such an absurdly early school starting age. These tests are driven by unprocessed and projected adult anxieties, and have nothing to do with a holistic understanding the nature of the young child. Countries which are at the top of the PISA international league tables wouldn’t dream of having such baseline tests at four - to them, it would be seen as unnecessary and abusive.’
Neil Leitch, chief executive of the Pre-school Learning Alliance, said, ‘We are very pleased to hear that the NUT have voted in support of a boycott of reception baseline tests, and fully support this decision.
‘The Government must accept that it has made a serious error in judgement here, and start engaging with parents and educational professionals to ensure that children are adequately - and appropriately - supported at the start of school and beyond.’