Teaching unions have criticised David Cameron's "war on mediocrity” in schools as "self-serving nonsense" that shows the government is "bereft of ideas".
Thousands of schools rated “requires improvement” by Ofsted could face enforced academisation or leadership change under plans to be announced today by the prime minister.
Any school placed in this category will be put under new leadership unless it can show it has plans in place to bring about rapid change, Mr Cameron will reveal in a speech in London.
But Kevin Courtney, deputy general secretary of the NUT teaching union, said it was "time that this emperor’s new clothes approach to education stopped".
The move follows a report published by the Commons Education Select Committee last week, which argues that there is not yet sufficient evidence to conclude whether the introduction of academies and free schools has had any effect on raising standards across the system.
Mary Bousted, general secretary of the ATL teaching union, said: “Faced with these uncomfortable findings, David Cameron has decided to plough ahead, doing more of the same…
"This is a government which is bereft of ideas. When will politicians stop declaring war on schools? It doesn't help their image with parents, the public or with teachers who see their motives for what they are: self-serving, publicity-seeking nonsense.”
Today's announcement by Mr Cameron comes as education secretary Nicky Morgan dropped strong hints that the 5-16 schools budget would continue to be protected under a future Conservative government.
However, she admitted that the 16-18 education budget, which has already faced substantial cuts under the coalition, would not be ring-fenced.
Mr Cameron is expected to announce today that failing schools will be at risk of being taken over by high-performing neighbouring schools or sponsors.
“Coasting” schools will automatically be considered for academy status and must set out plans for improvement that are deemed to be credible by the regional schools commissioner if they want to continue under their current leadership.
"As parents we're hard-wired to want the best for our kids,” the prime minister will say. “No one wants their child to go to a failing school – and no one wants to them to go to a coasting school either.
"So this party is clear: just enough is not good enough. That means no more sink schools – and no more 'bog standard' schools either. We're waging an all-out war on mediocrity, and our aim is this: the best start in life for every child, wherever they're from – no excuses."
The reforms build on existing powers that allow failing schools to be converted into academies. Some 1,200 schools have made the transition.
Speaking on the BBC’s The Andrew Marr Show yesterday, Ms Morgan said she was "absolutely fighting for the schools budget to be protected" but did not commit to similar protections for early years or further education.
Ms Morgan has also announced plans to make all primary school children in England learn their times tables up to 12 by heart, as well as carry out long division and complex multiplication.
Pupils will be expected to pass tough tests before leaving primary school as part of a "war on illiteracy and innumeracy", according to the education secretary.
As well as demonstrating mathematical skills, pupils will have to pass a writing test by showing they can use "accurate punctuation, spelling and grammar". Under the plans, by the time they leave primary school all 11-year-olds will know their times tables, be able to read a novel and be able to write a short story.
Ms Morgan said: "I think that's what parents and families would expect as a minimum from our exam system.”
'No evidence' academies and free schools raise standards, say MPs - 27 January 2015
Conflicts of interest are 'common' in academy trusts, study warns – 17 September 2014
Academy chain criticised for providing poor education – 18 July 2014
Academy conversion does not raise primary test results, analysis suggests – 7 May 2014