Nick Clegg will launch a dramatic attack on Michael Gove's "ideological" free schools policy in a speech next week, and remind voters that the two coalition parties have differing visions on education reform.
The Deputy Prime Minister is to open dividing lines with the Tories by insisting all teachers should be qualified, and the national curriculum should be taught in every school.
"I'm proud of our work over the last three years to increase school autonomy, which, in Government with the Conservatives, has been through the academies programme," the Liberal Democrat leader will say.
"And it is Lib Dem policy to give all schools, whether they are academies or not, those same freedoms to attract and reward excellent teaching, set their own term dates and vary their school day.
"We believe greater autonomy enables school leaders to take responsibility in those areas where they know what's best for their pupils, whilst also giving them the freedom to innovate.
"But it shouldn't surprise you if I say that, although we work well with the Conservatives, our two parties still have differences of opinion, some strongly held.
"Looking to the future, there are aspects of schools policy currently affected by the priorities of the Conservative Party which I would not want to see continue.
"For example, whilst I want to give schools the space to innovate, I also believe every parent needs reassurance that the school their child attends, whatever its title or structure, meets certain core standards of teaching and care. A parental guarantee, if you like.
"Parents don't want ideology to get in the way of their children's education.
"They don't care about the latest political label attached to their child's school. What they want, and expect, is that their children are taught by good teachers, get taught a core body of knowledge, and get a healthy meal every day."
In the address at a school in London, Mr Clegg will ask: "What's the point of having a national curriculum if only a few schools have to teach it? Let's teach it in all our schools.
"And what's the point of having brilliant new food standards if only a few schools have to stick to the rules? Let's have quality food in all our schools.
"That's my philosophy. Diversity amongst schools, yes. But good universal standards all parents can rely on too.
"And, frankly, it makes no sense to me to have qualified teacher status if only a few schools have to employ qualified teachers."
Mr Clegg will say that over the last decade there has been a "revolution in the way in which we've recruited and trained our teachers", including schemes such as Teach First and Schools Direct.
"What all of these routes have in common is that at the end of them you're recognised as a qualified teacher," he will add.
"And I want every parent to know that their child will benefit from this kind of high quality teaching.
"That's why I believe we should have qualified teachers in all our schools."
Labour has welcomed the Deputy PM's new stance. In an interview with the Observer, the shadow education secretary Tristram Hunt said: "I'm delighted Nick Clegg has realised the dangers of an ideologically driven schools policy. We would be happy to work with him to reintroduce accountability, proper standards and qualified teachers in all our schools across the country."