There is nothing surprising about New York City Mayor Bill de Blasio’s decision last week to rescind a deal struck last year to let the Success chain of charter schools to move three of its schools into traditional district buildings. Dropout Nation tried last year to give de Blasio the benefit of the doubt over his anti-charter school sentiments. But since moving into Gracie Mansion this past January, de Blasio’s moves — including a proposal to divert $210 million in funds slated for charter school construction projects, and the implementation of a formal ban on allowing co-locations — has all but proven that the mayor intends of putting the kibosh on the expansion of school choice throughout the city.

Certainly de Blasio’s decision, which damages the educational prospects of 7,000 children attending the three schools, belies his proclamations that he wants to build brighter futures for all Big Apple kids. At the same time, charter school advocates and other reformers have to do more than bemoan and protest de Blasio’s move. They must move boldly and decisively to build the political and financial support needed to advance systemic reform in spite of the mayor’s opposition. This includes moving away from space-sharing deals between charters and traditional district schools and toward more-sustainable approaches for obtaining the buildings they need to serve children in their care.

The move to rescind Success’ space-sharing agreement with the city came amid de Blasio’s move to review predecessor Bloomberg’s move last year to allow 17 charters (along with 32 traditional district schools) to share space in half-empty school buildings. The mayor and his chancellor, Carmen Fariña, decided to keep agreements with 14 of the charters in place (including five of the eight schools Success planned on opening and moving into the buildings). But the administration moved to rescind a deal with Success for three schools. Why? Supposedly because Success’ co-location plans for the three schools scored poorly in four categories used to judge the space-sharing arrangements — including whether the schools (which would have served less than 250 children) could provide what the city considers to be needed support services for them, and whether the city would have had to spend too much on construction (and thus, use dollars de Blasio is designating for his Pre-K initiative) to accommodate the charters.

Given the subjectivity of de Blasio’s criteria for judging the already-approved space sharing arrangements, it’s a shock than any of the 17 schools were approved at all. But then, that’s the point. By subjecting the plans to another review, de Blasio is making clear that he will use any tool at his disposal to put an end to charter school expansion. The fact that de Blasio took aim at Success, one of the city’s  biggest charter operators in the city and one of the most politically-vocal to boot, is a way for the mayor to put a chilling effect on any opposition to his plans from others in the charter school movement. Small charter operators who lack the fundraising and political means to challenge de Blasio, are now in the unenviable position of having their most-influential opponent also be chief executive of their landlord.

But the political is also the personal. In targeting Success, de Blasio also deals a blow to Moskowitz, a sharp-elbowed rival of the mayor dating back to the days when both sat on the Big Apple’s city council (and the education committee Moskowitz chaired). Since June, when de Blasio called out Moskowitz by name as one of the charter school operators he thought shouldn’t “get free rent” in city school buildings, the two have gone at each other publicly; de Blasio is likely still miffed over the move by Success and other charters last October to organize a rally calling him out for opposing choice for poor and minority children he claims to want to help. Sure, de Blasio couldn’t outright rescind all eight of the space sharing deals already struck with Success. But in tossing out three schools, the mayor has made it clear that he will work diligently to toss big-named charters out of traditional district buildings. More importantly, he has also signaled that this is the first step towards evicting all charters by the end of his tenure.

But reformers can’t just be fixated on de Blasio’s latest decision. The fact that several city council members chided the mayor for keeping arrangements in place with 14 of the 17 charters reviewed should also be troubling. Why? Because mayoral control of traditional districts also means that city legislators will also play their parts in structuring education policy and school operations. With de Blasio lacking unquestioned support from all sides for his education agenda, the council will play an even more-prominent role in education decision-making than it did during Bloomberg’s tenure. This plays well into the hands of the AFT affiliate, whose ground game has always been stronger than that of reformers. After losing court battles it lodge with the help of the NAACP’s New York State affiliate to stop Bloomberg’s space-sharing arrangements with charters, the AFT has spent plenty (including $450,726 last year through its super-PAC on 34 council races) to gain support within the city council. One can imagine AFT local boss Michael Mulgrew, currently in a (so far successful) battle with with AFT Empire State boss Richard Iannuzzi over control of the state affiliate, will quietly push council members to pass a bill that will end existing charter co-locations within the next year.

Yet charter school operators and advocates in the Big Apple can’t just worry about the politics. The moves by de Blasio serve to remind them of the reality that charter schools cannot continue to be dependent on space sharing arrangements with traditional districts.

Sure, the arrangements have been necessary in order to expand high-quality school options for children, especially those from poor and minority backgrounds in Harlem and the rest of the city still served poorly by the (slowly improving) traditional district. After all, unlike their colleagues in other cities such as Indianapolis and New Orleans, charter school operators in New York struggle mightily to find affordable real estate that can serve students properly. Given that charters are public schools (and, thus, are as entitled as traditional districts to using taxpayer-funded buildings), and the reality that many schools in Manhattan and the Bronx operate at less than full capacity, it just makes sense for charters and traditional district schools to share space.

But as de Blasio’s move has shown, such arrangements can expose charters to the kind of arbitrary and capricious decision-making that makes it difficult for operators to provide high-quality teaching and curricula to the children they serve. It can also be damaging to efforts to expand choice overall, creating skittishness among families, who count on schools to be stable places in which their kids will learn. More importantly, by counting on the Big Apple to provide space, charter school operators aren’t working diligently as their counterparts in other cities on developing funding sources (including dedicated state dollars for capital expenditures and donations from philanthropists) they can count on for constructing buildings they control.

Once again, it is important for charter school advocates and other reformers in the New York City to once again make the case for systemic reform — and look to other approaches to transforming education in big cities — regardless of who occupies City Hall. This includes working hard in the grassroots, especially with community groups, immigrant households and single-parent families in the city who benefit the most from charter school expansion, to put pressure on de Blasio and city council members to attend to their concerns. Groups such as the New York branch of StudentsFirst should be organizing voter registration drive right now. Passing a Parent Trigger law at the state level, which would allow families to take control of school buildings and launch their own charters (as well as work with existing operators, if they so choose) should also be on the agenda.

At the same time, Big Apple reformers must work with charter school operators to embark on a capital campaign to acquire existing buildings, construct new schools (when possible), and ultimately, move out of traditional district spaces. One can easily imagine the Walton Family Foundation teaming up with outfits such as Building Hope, an organization working throughout the country on charter school building efforts, to embark on developing a school campus in South Ozone Park where several charters can share space. Lobbying Gov. Andrew Cuomo and other state leaders to provide dedicated funding to charters for their capital activities — or even create a fund that lends money to charters for construction activities — also makes sense.

Charter advocates within the city should also embrace online learning options as a way to deal with space issues. In an age in which virtual learning is possible and can be provided with high quality, especially in New York City (where broadband is plentiful), there is no reason why charter school operators continue to think about education as being something provided only in buildings.

Mayor de Blasio’s move against charter schools offers reformers opportunities to sustain reform. Now it is time for them to embrace it.