Estelle Morris is worried that pupils are struggling when they move up to secondary school

And she warned that disaffected youngsters were "disappearing from the education system and then re-appearing in the courts".

It was this age group that was responsible for much of the surge in crimes such as street robbery, she said.

Emphasising the links between educational failure and teenage crime, she said that 50% of youngsters serving custodial sentences had a reading age of 11 or under.

And that a quarter of these young lawbreakers had levels of numeracy which were 10 years below their actual age.

'Underperformance'

The lecture on the need to radically improve standards for 11 to 14 year olds was presented by the Department for Education as a "landmark speech".

This blueprint for reform pledged to tackle "systematic underperformance" in these "middle years".

There were 200,000 pupils a year failing to make the grade in English, maths and science - and many pupils were getting worse rather than better when they moved up from primary school.

These early years of secondary education were the "missing piece of the jigsaw", she told an audience at the think-tank, Demos.

And this "big vision" might be seen as Estelle Morris's attempt to leave a tangible impression on the education system - in the way that her predecessor, David Blunkett, was associated with reforming primary schools.

Unruly behaviour

Among the key challenges facing these "forgotten years", she said, was to find ways to motivate pupils and to prevent unruly behaviour.

And schools also had to respond to changes in young people's lives, such as "less cohesive" family structures and the arrival of physical maturity much before a corresponding emotional maturity.

Ms Morris said the achievement of 11 to 14 year olds had been neglected in the drive to raise standards in primary schools and at GCSE and A-level.

Looking ahead to the future, she suggested that the two key "milestones" in secondary education could become 14 and 19, suggesting that the exams taken by 16 year olds will be less significant.

A pamphlet - Transforming Secondary Education: The Middle Years - spells out how the department aims to boost standards in the first three years of secondary education.

The strategy is based on three pillars - raising standards through better quality teaching, tackling bad behaviour and increasing choice.

Increased choice would give schools greater freedom to develop new approaches to the national curriculum, the organisation of the school day, the grouping of pupils and the use of teachers, the document says.

In her speech, the education secretary said that the secondary system had been too uniform and inflexible and that there needed to be different types of schools for a diversity of needs.

Schools should work in closer collaboration with each other to share best practice and teachers should develop interactive lessons so that learning becomes less prescriptive.

In time, the government wants to see the term "Key Stage 3" for the 11 to 14 age group dropped in favour of "middle years", saying this is more meaningful for parents.

The Conservatives said that the failure of pupils entering secondary schools showed that the primary sector was not succeeding in preparing pupils.

"If the secretary of state has identified big problems with eleven year olds, it suggests she has been exceptionally complacent about the primary sector," said the Shadow Education Secretary, Damian Green.

"If 11 year olds cannot cope with secondary education then we urgently need to look at how they have been prepared for it.

"It seems that the constant interference by government in the details of teaching is not achieving the desired results, and even Estelle Morris is now admitting this."