New York City Mayor Bill de Blasio has announced he is backtracking on existing agreements that allow several charter schools to share space—or co-locate—in the same buildings with regular public schools in the city.

The announcement is expected to impact nearly 700 charter students, including some from one school that is already operating in a regular public school building . That school is Success Academy's Harlem 4, which charter supporters say is one of the top-performing schools in the district and the state.

With his announcement, Mayor de Blasio is making good on a campaign promise. During last year's election, he repeatedly said he did not support the co-location policies of his predecessor, former Mayor Michael Bloomberg, and that he would review the proposals approved last fall in the final days of Bloomberg's administration.

"As a public school parent, I am committed to a fundamentally different way of making decisions about co-locations," said Mayor de Blasio in a statement. "We made clear from the outset we would carefully review all of the proposals rushed through in the waning days of the past administration. We set out consistent, objective criteria to protect school communities from unworkable outcomes. And today, we are taking the best possible path forward, rejecting those proposals that do not meet our values, and working with school communities on those proposals that can be implemented responsibly."

Of the 49 proposals previously approved by Bloomberg, Mayor de Blasio's office has made decisions on 45 schools, deferring decisions on four of the proposals for schools opening in 2015-16. The decisions were made public in a New York City Department of Education memo. While the vast majority of the space-sharing plans were approved to move forward, nine were withdrawn by the de Blasio administration, including three plans for Success Academy schools, including Harlem 4.

One proposal, for the American Dream Charter School, has been revised—it will now be allowed to open three sections per grade instead of the four sections per grade it was originally granted in order to better fit the space.

The administration says it will be adopting an engagement process for communities regarding the changes that it promised will "look very different than it has in the past."

Charter school advocates are considering this the first major blow to the charter community there.

"Kicking one of the state's top-performing schools out of its building and leaving three other schools without a building is nothing short of outrageous," said Nina Rees, the president and chief executive officer of the Washington-based National Alliance for Public Charter Schools, in a statement. "At the school already serving children, Success Academy's Harlem 4, 83 percent of the students passed the state math exam last year, putting it in the top 1 percent of all schools in the state. Why would anyone want to stop that kind of student achievement?"

But others praised the move, such as the city's teachers' union, United Federation of Teachers, whose president Michael Mulgrew, said in a statement, "I'm glad the DOE has taken an important first step in vetoing some particularly troublesome pending co-locations."

New York City schools chancellor Carmen Fariña responded by saying, in the Department of Education memo, "if there is one thing school communities should know, it's this: We're going to do things differently. Today, we are turning the page on the approach of the past. We are going to listen and be responsive like never before, and that will be reflected in everything we do."

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