They have been praised by politicians for giving teachers the freedom to innovate and reach higher standards, but England's free schools and their charter school forebears in New York City are suffering serious setbacks.
Charter school providers in New York have seen their fortunes change dramatically since the election of Bill de Blasio as the city's mayor. He has announced plans to redirect funds to pay for a pledge to improve early years provision.
The decision, coupled with a 12-month moratorium on allowing new charter schools to open in the same buildings as existing public schools, has led providers to claim that the new mayor is "killing" the expansion of the programme.
Bill Phillips, president of Northeast Charter School Network, said this week that the changes being introduced by Mr de Blasio, not least the decision to pull $210 million of capital funding, meant that some providers were no longer seeking to open new schools in New York.
"If New York City has been a national model for growing charters, I think Mayor de Blasio is laying out a blueprint for killing charter expansion," Mr Phillips said.
By pulling funding, the mayor wanted to make it "more difficult for existing charters and make sure there's no expansion of chartering in New York City", Mr Phillips added. "We have some of the best operators in the country in New York City, and I know that operators are starting to look elsewhere."
James Merriman, chief executive of the New York City Charter School Center, told TES that charter schools wanted to be involved in the push to improve early years education. "If the administration is interested in results, they will make sure high-performing charter schools are fully included. Otherwise, it will be clear that their move is more about ideology and pleasing the teachers' union than about helping our most at- risk children."
New York has become the epicentre of the school reform agenda in the US, and England's education secretary, Michael Gove, has borrowed heavily from the charter movement - with its emphasis on schools being run independently of local government - for his own free schools policy.
But Mr Gove's free schools are also hitting stumbling blocks: two are facing imminent closure because of poor standards. Last week, the Department for Education ordered Al-Madinah Free School in Derby to shut its secondary provision after two inadequate ratings from inspectors. This follows a decision just before Christmas to close the Discovery New School in West Sussex.
The future of another free school, the King Science Academy in Bradford, is hanging in the balance as it undergoes a criminal investigation after allegations of fraud.
Natalie Evans, director of the New Schools Network, a charity that supports groups wanting to establish free schools, has said there is "no question" that more failures will follow. This is because of "legacy issues from the early days" before a more robust selection process had been put in place, she told TES.
Laura McInerney, a Fulbright Scholar studying education policy at the University of Missouri, said the biggest difference between the reforms in the US and in England was the pace of change. "Nowhere in the US moved as quickly with their charter schools as England has with its free schools," she said. "Everyone has acknowledged in the UK that the first phase moved too quickly, where there was less due diligence done."
Criticism of free schools is understood to be central to tensions between England's schools inspectorate Ofsted and the Department for Education. On Monday, the Labour Party's education spokesman Tristram Hunt claimed that Mr Gove was "purging" the watchdog of board members because it was inspecting free schools "without fear or favour".
The DfE said that the vast majority of free schools were performing well. "But where we have found failure we have acted swiftly and decisively," a spokesman added.