The leader of teaching union the NUT has given her strongest indication yet that her members could boycott Year 6 Sats tests again next year.
General secretary Christine Blower said heads who took part in this year's boycott felt "very strongly that they don't want to do the tests again", after Education Secretary Michael Gove announced they would still be going ahead in May 2011.
Senior officials at the union will meet heads' union the NAHT next week to discuss their next move, including a possible ballot over whether headteachers should boycott ordering in the exam papers.
This year's boycott was criticised by some heads for being announced too close to the exam dates. Many felt they had to go ahead with the tests, despite being opposed to them, as they did not want to disappoint the children.
If heads knew the boycott was going to happen as early as the autumn, when the papers are ordered, they say they could avoid unnecessary preparation and build-up.
Ms Blower told The TES: "We have not ruled out a boycott, and we are having ongoing discussions about this."
She added there could be an "early intervention", suggesting a ballot could go out to school leaders over a refusal to order the test papers in the next few months.
The NAHT, which took part in this year's action, has remained mute on whether it will attempt a second boycott, but sources suggest it could join in if talks with Mr Gove prove unsuccessful.
The impact of the boycott would depend strongly on the participation of the heads' union, as it represents most primary leaders.
Figures released by the Government last week suggested that 4,004 - or 26 per cent - of the 15,515 eligible primaries did not take the tests this year.
The participation rate largely reflected the ballot before the action, when 29 per cent of eligible heads voted in favour of a boycott.
Ms Blower spoke out as the NUT and the Association of Teachers and Lecturers (ATL) launched a joint paper today, outlining an alternative regime to external testing and league tables.
The two unions are calling for Sats to be replaced by a system of teacher assessment, and say individual schools should be judged by the progress made by pupils of all abilities.
They say their teacher assessment could be moderated by nationally accredited experts, and sample testing would allow the Government to monitor the progress of the country as a whole.
The paper mirrors a similar one published by the NAHT earlier this year, but the two unions say it offers the perspective of classroom teaching staff.
Mary Bousted, general secretary of the ATL, said her union had no plans to mandate a boycott, but is still calling for the system to be overhauled. She said: "We know that the intellectual argument is won - our job is to put forward an alternative.
"The system's dirty little secret is that the tests are inaccurate. The more perverse incentives you put into the system, the more you teach to the test. Teacher assessment comes in at lower scores than testing - teachers don't over-inflate scores."
Ms Blower added that the league tables were not necessary for parents to judge schools, as nothing was more effective than actually visiting them and seeing what they were like.
- Original headline: Blower hints that NUT could repeat Sats boycott next year