New York City has become the promised land for the charter school movement, attracting politicians from around the world wanting to learn the secret of the schools' success.
But this week, the future for charter schools in the city became a whole lot gloomier after millions of New Yorkers went to the polls to vote for their new mayor, handing a landslide victory to Democrat candidate Bill de Blasio.
Mr de Blasio's win is likely to presage a significant move to the left and a much tougher time for charters. Among his pledges, the new mayor has said that he will impose a year-long moratorium on charter schools - which are publicly funded but independent - opening in the same buildings as public schools. He has also vowed to charge rent to the dozens of charters that have already done so, potentially stripping millions of dollars from their budgets.
The New York City Department of Education has been a major advocate of "co-location", where charters are allowed to open in the same buildings as public schools. More than 60 per cent of the city's 183 charters operate under this agreement.
But if Mr de Blasio's proposals are implemented, any charter intending to expand or any new charter hoping to open in a district school would be prevented from doing so by city officials for the next 12 months.
Unsurprisingly, the plans have prompted opposition from charter school chains and also from thousands of parents and students who support the schools.
Dave Levin, co-founder of the Knowledge Is Power Program (Kipp) chain of charters, which operates 10 schools in New York City, told TES: "As public schools, charters should continue to have the same access to free school space as any other public school in New York City.
"At Kipp, we are eager to collaborate with the next mayor to put even more underserved kids on the path to and through college."
Mr de Blasio's other policies include raising city taxes in order to pay for universal preschool provision and a pledge to prevent struggling public schools from closing down.
The position of New York mayor is arguably one of the most influential in American public life, and Mr de Blasio's victory marks a significant shift for the city's voters after the incumbent Michael Bloomberg - a former Republican who stood as an independent - and his Democrat-turned-Republican predecessor Rudy Giuliani.
Mr de Blasio's stance on charters is at odds with that of many politicians around the world, not least England's education secretary Michael Gove and US President Barack Obama, both of whom have lent their support to the idea.
Thousands of parents and students have also voiced opposition to Mr de Blasio's plans, staging a protest last month in which 20,000 people marched across Brooklyn Bridge in support of charter schools.
But New York's main teaching union - the United Federation of Teachers (UFT), which is affiliated to the American Federation of Teachers - belatedly endorsed the De Blasio campaign in September, bringing with it serious financial and campaigning clout.
Speaking at a campaign rally for Mr de Blasio last week, the UFT's president, Michael Mulgrew, heralded the expected victory of the Democrat candidate as a new dawn.
"We have a new day coming for New York City," Mr Mulgrew told a cheering crowd, before asking, "Who's going to make sure this city is for everyone?", to which the crowd called back, "De Blasio".
In response to Mr de Blasio's critics, a spokesman said the policy to charge rent would simply bring New York City into line with the rest of the country.
"(Mr de Blasio) will work with all our schools, but he believes that well-resourced charter networks should pay for the use of school space, as charter schools do across the country," the spokesman told the Associated Press this week. "He'll put a moratorium on co-locations until we can better assess their impact."