Image copyright Reuters Image caption The watchdog warns about inconsistency in helping schools to improve

There are 1.6 million pupils in England who are still not getting a good education but there is a failure to deal with under-performing schools, a spending watchdog has said.

A report from the National Audit Office said there was a lack of consistency in tackling under-performance.

Margaret Hodge, chair of the Public Accounts Committee, said she was "appalled" at the lack of progress.

The Department for Education said schools "have been transformed".

A DFE spokeswoman said the report's conclusions were "not supported by the facts" as the proportion of schools rated by Ofsted as good or outstanding had risen from 68% to 81% since August 2010.

Head teachers also argued that the watchdog's report was painting an excessively "bleak picture" of school standards.

Inspecting trusts

The National Audit Office has warned that despite £382m being spent each year on monitoring schools and interventions, there are weaknesses in efforts to raise standards.

In particular it raised questions about how much the Department for Education knows about problems at school level, in a system with increasing autonomy for individual schools and academy chains.

"Some academy sponsors are very successful, but the department does not yet know why others are not," said the National Audit Office.

It drew attention to concerns, voiced by Ofsted chief inspector Sir Michael Wilshaw, that the watchdog cannot inspect academy trusts.

"Ofsted is unable to inspect sponsors and multi-academy trusts so there is no independent source of information about the quality of their work," said the spending watchdog.

Concerns over the oversight of academies emerged in the wake of the Trojan Horse scandal in Birmingham - and the report warned of a lack of checks on governors to "prevent risks such as entryism" - where a group of like-minded individuals infiltrate an organisation aiming to take it over.

"Greater school autonomy needs to be coupled with effective oversight and assurance. The department has made some improvements but has further to go," said Amyas Morse, head of the National Audit Office.

"There are significant gaps in the department's understanding of what works," he said.

'Red tape'

The report highlighted the 1.6 million pupils in schools which have inspection grades of either "inadequate" or "requires improvement".

Mrs Hodge said the figures from the spending watchdog showed it is "hard to see how formal interventions make any difference", with 52% of schools not improving Ofsted grades after intervention and 59% improving without any intervention.

She said it was a "sorry state of affairs when the department has to rely on whistleblowers to spot declines in school performance".

But head teachers rejected the findings.

"The reality is nowhere like the bleak picture painted somewhat dramatically today," said Malcolm Trobe of the Association of School and College Leaders.

"The evidence from Ofsted is that schools are improving year on year," he said.

'Huge progress'

David Simmonds, chairman of the Local Government Association's children and young people board, said councils needed to be freed from the "red tape" that delayed their intervention.

"Councils want to intervene more quickly, but decades of giving schools "greater freedom" and "protecting" them from council interference means that local authorities now have very indirect and bureaucratic ways to tackle poor performance and improve schools."

Christine Blower, head of the National Union of Teachers, said the findings were a "damning verdict on a government obsessed with change for change's sake and poor on accountability".

Labour's shadow education secretary Tristram Hunt said the report was an "utterly damning account" of the government's failure in education.

"It makes clear that the government has no plan for tackling poor standards and simply does not know who is responsible for overseeing schools and the safeguarding of children."

But a Department for Education spokeswoman said "huge progress" had been achieved in improving schools.

"England's schools have been transformed over the past few years with 800,000 more children now being taught in good or outstanding schools since 2010.

"This is a great achievement but we would be the first to admit that the job is not yet done.

"Any child being taught in a failing school is an opportunity lost, which is why we have intervened in more than 1,000 failing schools over the past four years - pairing them up with excellent sponsors to give pupils the best chance of receiving an excellent education."