Too much testing in schools is eroding children's human rights, a union leader suggested.
Under international law children have the right to a broad education, not just to pass exams, Christine Blower, general secretary of the National Union of Teachers, said.
National curriculum tests - known as Sats - are not part of a rounded education, she said.
The NUT, along with the National Association of Head Teachers (NAHT), is currently halfway through a ballot over a boycott of this year's tests.
In a speech at the NUT's annual conference in Liverpool today, Ms Blower said the government is signed up to the UN Convention on the rights of the child.
She said: "Some of the Articles are about basic human rights, these include the right to a name, the right to be safe and the right to be educated in the round, not only to pass exams.
"I think that's a pretty high authority on which to rely when we say the Sats regime is wrong and it must go."
She also told delegates: "The NUT says 'yes' to risk taking and exciting approaches to learning and 'no' to children as little bundles of measurable outputs."
Speaking after the conference, Ms Blower said Sats seem to be designed just so that children get to a particular level.
She insisted that this was not the basis for the trade dispute, and that the boycott was focused on headteachers being undermined by the creation of league tables using Sats results.
Sats in English and maths are due to be taken by around 600,000 11-year-olds in the week beginning May 10 - less than a week after the country goes to the polls. The ballot closes on April 16, and a result in favour means a boycott could be the first battle a new government - of whichever party - has to face.
The Convention says that every child should have a right to education and encourages different forms of secondary education, including general and vocational as well as compulsory primary education.
Ms Blower's speech came as MPs reiterated their concerns that national curriculum tests encourage schools to "teach to the test".
The Schools Select Committee report, From Baker To Balls: The Foundations Of The Education System, says: "We reiterate that we are not opposed to the principle of national testing. Where we do have concerns is the use of the same test for a range of purposes that cannot all be met at the same time.
"If pupils' attainment is used to judge teachers and schools, teachers cannot be expected to be dispassionate assessors of that attainment, and teaching to the test is a likely consequence.
"We therefore have reservations - as does Ofsted - about the effects of national testing in concentrating teachers' efforts upon certain areas of the national curriculum."
The NUT and the NAHT want to see Sats replaced by teacher assessment and argue the tests are bad for children, teachers and education, and cause unnecessary stress. They also want to see school league tables abolished. Both unions conducted indicative ballots at the end of last year, to assess support for a boycott.
NAHT general secretary Mick Brookes said at the weekend that if this support was replicated in the full ballot, between 6,000 and 7,000 primary schools could be involved in the boycott. There are around 17,000 primaries in England.