But Government says it is to ensure continuity and nothing to do with poor results in December.
The standard required to do well in a new national test is to be lowered, The TES can reveal.
The change, which affects single-level tests in English and maths, has been made public after pupils performed badly in the first round of pilots in December. However, Whitehall officials said the decision to change the format was made before pupils sat them.
Single-level tests could replace Sats within two years. Initially, it was envisaged that pupils would have to demonstrate they were working securely at a national curriculum level for them to be awarded that level. This was the model used in December when pupils in 411 schools took the tests.
In the next round in June, pupils will only have to demonstrate that they have just reached a level. The Department for Children, Schools and Families (DCSF) said the decision would align the standard of the single-level tests with Sats.
Many teachers appear to be supportive of aspects of the pilots, although The TES has found it difficult to find out because some schools have been told not to speak to the media.
This week a National Union of Teachers survey of 34 members in schools taking part found a quarter believed the tests support teaching and learning. A quarter said they would not, with 48 per cent unsure.
Geoff Gait-Carr, headteacher of Calton Junior School in Gloucester, said: "On the whole we think it is a good idea."
A new form of teacher assessment is being used to decide when pupils are ready to take the tests. But many staff say this is adding to their workload. Graham Horton, head of Woolaston primary in Gloucestershire, described the process as "extremely bureaucratic with masses of paperwork".
The revelation of the lowering of standard will lead to fresh questions about the Government's testing regime. Experts doubt whether a pupil just achieving a national level should be encouraged to move up to the next level.
The TES disclosed two weeks ago the unexpectedly bad results produced when the new tests were taken by 22,543 pupils in 411 schools in December.
The new assessments are set at single national curriculum levels, with teachers entering pupils for them up to twice a year when they think the pupil is ready.
A DCSF spokeswoman said: "In terms of the change from secure to threshold, yes we have changed that. We decided to do that before any pupil sat the tests, and before we had any results. We did it to secure continuity of standards with the current national tests. We needed level 4 or 5 achieved in the single-level tests to mean the same as it does in the key stage tests.
The Government has yet to release the results of the December tests after saying it had uncovered "unexpected patterns" in the scores. This week, David Gee, managing director of the National Assessment Agency, told a conference that eventually he would like pupils to be able to take national tests at any point in the year. There is no immediate prospect of this happening.
The evolution of single-level tests
The original plan
In December's test round, examiners decided on the minimum, or "threshold", number of marks associated with a particular national curriculum level.
They then said that pupils had to clear this hurdle comfortably to demonstrate that they were secure in reaching this standard. As a result, the pass mark for the test was higher than the "threshold" score.
The tests were set up this way to provide a robust check that a teacher's assessment of a child's ability - which is used to decide whether or not to enter that child for each single-level test - is reliable.
They were also designed to avoid pupils moving on to a harder test before they were confident in their performance at the easier level.
Now any child just receiving the "threshold" score will be deemed to have achieved the level.
David Gee, managing director of the National Assessment Agency, spoke of the change at a Qualifications and Curriculum Authority event this week.
He said the move would bring the new tests into line with Sats, where pupils only have to achieve the minimum standard to gain their level.