Ministers have halted the controversial and troubled "single-level tests" experiment a year earlier than was planned.
The tests, designed to relieve pressure on teachers and pupils and potentially replace Sats, have not been completely killed off and will be considered under a forthcoming review of national curriculum assessment.
But the decision to cancel a 201011 extension to the trial casts huge doubts over their future.
Unions welcomed the end of trial, saying single-level tests (SLTs) had merely encouraged teaching to the test and a narrowing of the curriculum.
Russell Hobby, National Association of Head Teachers general secretary, said: "The last thing our schools need is another inaccurate, unreliable testing system. The current one is bad enough."
But maths SLT results from as many 225 primary and middle schools that took part in the three-year pilot will still be used to compile this year's league tables, raising the spectre of unfair comparisons.
The SLT pupils will have been given up to four attempts to achieve their best possible mark over two academic years, while pupils sitting conventional Sats will have had one.
SLTs were first proposed by the Labour government in 2007 as ministers sought to address disaffection in schools over the Sats regime.
The idea was that a series of tests would be developed, each testing a single national curriculum level.
Pupils could then be entered for whichever test was appropriate whenever their teacher felt they were ready, in one of two testing "windows" every academic year.
But it was immediately pointed out that the idea was likely to lead to a major rise in high-stakes testing.
It also suffered from major technical problems as officials struggled to develop tests that examined a single level but were appropriate for pupils of different ages.
Last year it emerged that the Government had continued with the trial despite warnings from the Qualifications and Curriculum Authority and five independent academics of "substantial and fundamental" problems and that the central aim was "very probably impossible" to achieve.
Unions started advising schools to pull out of the pilot and by March this year more than one in four had done so.
Despite this, officials said they needed to extend the pilot because they had not learnt enough about how schools behaved with SLTs when they were being used to hold them accountable.
But this week schools minister Nick Gibb said: "The pilot has run for three years and that has allowed us to gain a sufficient amount of evidence about single-level tests that we do not need to continue the trials any further.
"This evidence, including evaluations of the pilot, will feed into the forthcoming review of assessment in primary schools."
Christine Blower, NUT general secretary, welcomed the news and said: "There was increasing evidence (SLTs) were resulting in teaching to the test twice a year and generating a great deal of unwelcome bureaucracy and cost to the school."
Ian Toone, from the Voice teaching union, said: "We hope that these tests will not be replaced with others. The next logical step would be to scrap the remaining key stage 2 tests."
225 - Number of primaries and middle schools that took part in the pilot.