Ruth Kelly is pushing for more consistent improvement in schools

In a speech on "raising the bar" in school standards, Ms Kelly says there are unacceptably wide differences in achievement by similar schools.

And she promised a White Paper which will enable swift action against schools which are failing.

"No change - or slow change - must no longer be an option," she says.

'Social justice'

In a speech to the Specialist Schools Trust, Ms Kelly says that parents will not "settle for second best".

"No school will be judged good if its performance is merely ordinary. No school will be judged to be strong unless pupils are judged to make good progress."

Promising a reform package in a White Paper in the autumn that would be "wide ranging and ambitious", Ms Kelly says the "drive for school improvement is a moral imperative. A drive for social justice".

She says that the inconsistencies in achievement in middle-ranking schools need to be addressed - and that schools must ensure that all pupils acquire the basics in English and maths.

The education secretary points to the gulf between the positive impact made by the most successful schools - and the lack of improvement by pupils in schools at the lower end of the scale.

"In the 20% of schools with the highest value-added, pupils are making nearly a year's more progress compared to those 20% of schools with the lowest value added. This means pupils in underperforming schools are losing nearly a year's worth of learning," Ms Kelly says.

'Letting down pupils'

The difference extends to individual departments within schools, she says, promising that more detailed performance information will show where "departments are letting down their pupils".

Where schools are failing, she says that decisions about their future must not be allowed to drag on for years - and promised that the forthcoming White Paper would address the need for rapid action.

"If the school's leadership is not up to the task, if the school requires major restructuring, if the governance needs changing - it does no one any favours to delay hard decisions.

"I am determined to ensure that firm and decisive action is taken with these schools. And I am determined to take that action as early as possible. No change - or slow change - must no longer be an option," says the education secretary.

Ofsted had found that last year 1,000 schools, about four-fifths of them primary schools, had not made sufficient progress between inspections - not failing, but simply not delivering higher standards for their pupils.

"This is the kind of 'coasting' - not improving for pupils and parents - that we want to tackle," says a Department for Education and Skills spokesperson.