Test results have pinpointed exactly where the current system is allowing pupils to fall behind or coast.
Each figure in the graphic represents 1 per cent of the pupils who took the national test in English for 14 year olds in 2005.
The light and dark blue figures making up the majority are the 74 per cent who reached the expected level five or above.
Among them are 26 per cent who progressed to level 6 and a further nine per cent to level seven.
Ministers hope the new "progress" tests and targets will ensure they continue to be stretched.
Among the 74 are another five per cent who were already at level 5 when they entered key stage 3 but have not progressed since. Existing targets give no incentive for schools to deal with this problem.
The next five per cent - the pink figures - are also "stuck", but are below expectations. They have achieved level 4 - meaning they can read fluently - so further progress in Levels achieved at KS3, 2005
* 5 or above ( results in 2000)
* 5 or above
* 4 (stuck)
* 4 (slow-moving) 5 target for 2007
* 4 (fast-moving)
* 4 (missing data)
* 2 or below
* Absent English should have been possible, the Government believes.
Officials visiting a sample of pupils discovered they had become demoralised and were never fully motivated throughout key stage 3.
Some had asked to be moved down a set and some were in "freefall", moving down several. But they did well with passionate and engaging teachers, who knew them well.
"Their failure was a slow falling off, not a sudden disengagement,"
officials found.JThey craved rewards, mentors and resented the talented, least able and disruptive pupils who got extra attention.
The Government hopes its new tests can help schools to spot these pupils and intervene before they fall behind.