in two months' time, nearly 500 schools will begin a pound;20 million trial of a system in which 7- to 14-year-olds will be given a national test whenever their teacher believes they are ready.
It marks potentially the biggest change to national tests since they were introduced in the early 1990s and could carry major implications for the way teaching is structured.
Perhaps most innovatively, individual tuition sessions will be offered to pupils struggling with English and maths. Controversially, the 10 hours' tuition they will receive will be spread over the whole of the key stage that is four years at KS2 and three at KS3. Some schools are considering opening on Saturdays to offer the extra hours.
And because the pilot schools will run the new system side by side with conventional tests, they will be able to choose from the better results, meaning they could get a league table bonus for taking part.
So, how will the scheme work? And will it be an improvement on national testing?
Teachers in 10 local authorities are about to find out as the trial begins. Next term, they will start building up for the first of the new system. Twice a year, in December and June, teachers will be given the chance to enter their pupils for a test in any or all of reading, writing and mathematics.
Each will last 50 minutes and cover only a single national curriculum level. Tests are available initially at levels 3 to 6. From next June, tests will also be offered at levels 7 and 8. All of the tests will be marked externally.
The system is effectively a hybrid of testing and teacher assessment, as teachers will use their judgment to decide when to enter their pupils .
Crucially, the National Assessment Agency, which is running the pilot tests, says they are meant to support teacher assessment.
"The purpose of the tests is to act as a confirmation of teachers' assessment judgments," headteachers in one of the trial local authorities heard at a presentation from officials at the Department of Education and Skills, as it was then called.
This represents a potentially radical shift. After national testing was introduced, it was meant to be given equal status with teacher assessment. But in reality, test data has always been given more weight by the Government.
Alongside the tests, the assessment agency will monitor the proportion of pupils making two levels' progress over the key stage. Schools will be under pressure to raise the percentage of children making this improvement.
At a meeting in one of the 10 local authorities, one primary said it already had all its pupils rising by two levels. To the astonishment of those present, the officials from the department told the school it needed to increase this proportion to 104 per cent.
The schools will also be handed pound;450 bonus payments for each pupil who began a key stage at below the Government's expected level but went on to make the required two levels' progress. But pupils will still be taking conventional national tests and their level will be determined by which of the two they do better at.
Controversially, this will also be the same for the school, meaning those in the pilot authorities will effectively have two alternative routes to league table success.
If the trial proves successful these progress tests could eventually replace the end-of-key-stage tests and form the basis of school league tables and targets in their own right.
It is this final aspect which has been the most contentious.
Although respondents generally welcomed the move towards teacher-informed assessment and an end to the burden of mass testing, there have been many concerns. Chief among these has been the danger of over-assessment. It is feared that teachers under pressure over results may push pupils to take tests too frequently.
Testing experts worry about the difficulty of designing a test covering only one national curriculum level, because of the fine judgments involved. There are also concerns that children may be pushed to take tests before they have become proficient in all areas of the subject.
Those making these points include testing experts at Cambridge Assessment, which runs three exam boards, and academics at the Assessment Reform Group. All welcome the fact that the tests are subject to trialling. But most want more than one model to be piloted.
The second aspect of the trial is equally innovative. Schools and local authorities are recruiting tutors to provide one-to-one coaching for 10 per cent of pupils in each local authority.
These are struggling pupils or those whose progress has stalled. They will receive 10 hours' tuition over the key stage.
Heads are recruiting teachers at their school, staff from neighbouring schools, retired teachers and private tutors to offer the sessions.
The tuition takes place after school, at breakfast time or even on Saturdays. Tutors are expected to be paid around pound;25 an hour.
Individual tuition: who gets it?
Key stage 2 Those who start at level 2b or below in literacy or numeracy.
Key stage 3 Those who start at level 3 or below.
Pupils who have not progressed from level 4 since Year 6 and are stuck or very slow-moving at KS3.
Those who are not on target to reach the expected level for their key stage or to progress by two levels during each stage.
Looked-after children who would particularly benefit from individual support.
Tuition will be available to 10 per cent of all KS2 and KS3 pupils in participating schools. So a typical six-form entry secondary might have funding for 45 pupils, while a school with two forms per year group might have funding for 20.
Local authorities taking part in the pilot tests are Bexley, East Sussex, Essex, Calderdale, Gloucestershire, Leicestershire, Liverpool, Solihull South Tyneside and Westminster.
Source: Presentation to heads by Whitehall officials
'We can offer personalised learning at the right pace'
Annette McStea, one of the first teachers to become a personal tutor under the new testing scheme, is convinced of the benefits of the one-to-one approach.
From September, Ms McStea (left) will be working with two KS2 pupils who are judged to be at risk of failing to make two levels' progress between Year 3 and Year 6.
Ms McStea, 44, a Year 6 teacher at Hadrian primary in South Shields, Tyne and Wear, will be paid around pound;25 an hour for providing the tuition in English and maths after school.
Staff sit down with the pupils and their parents beforehand to agree how to structure the tuition, which will be provided in 10 one-hour blocks.
"I have taught pre-test booster classes in the past," she said, "and the progress that pupils have made as a result has been impressive."
The one-to-one tuition would build on this approach, she said.
"I think it will help pupils who are in danger of being overlooked in the classroom if taught on a more traditional basis."
"It will give us the time to provide personalised learning at the right pace for the pupil, to focus on an area of need and to help the children to fulfil their potential."