It was the best early Christmas gift Michel Sidemion could have asked for — an offer of admissions from his dream school: Tufts University. A video capturing his moment of joy went viral over the weekend, shared around the world. The Bronx teenager is a senior and a member of the first graduating class at Success Academy High School of the Liberal Arts in Manhattan

For a generation now, charter school opponents have warned that these alternative public schools will spell doom for the American ideal of public education. It’s about time that they offer something more than anecdotes and theory to support their claims. More than two decades into the charter school experience, it’s clear that charters are not proving harmful to traditional public schools—and, if anything, are helping them do better.

What urban charters in general, and Success Academy in particular, have figured out is that the achievement gap is not, as some conservatives have speculated, genetic. Nor is it some ethereal “culture” that defies institutional design. It is the product of a confluence of policy and environmental factors that can be identified and remedied. The achievement gap results from a gap in health, nutrition, parental involvement, community expectations, an orderly school environment, exposure to vocabulary, and access to books, among other things. Urban charter schools have systematically identified the missing sources of support and supplied them.

As an elected representative who believes that a public official’s first duty is to their constituents, as a Bronxite who wishes for a solution and as a father committed to providing my daughters with the best education, I urge our city leaders to do the right thing by providing public charter school students across New York City with the space they need to learn – not just for one year, but for many years to come.

For parents and kids at Success Academy Cobble Hill, their three-year battle with the Department of Education for more classroom space isn’t a political exercise — it’s a daily anxiety. That’s because the high-performing charter school has never been provided with the promised space for students in grades five to eight within the district.

One school became 46. One hundred sixty-five students became 15.500. A tiny outpost in Harlem spawned brethren all across Manhattan, the Bronx, Brooklyn, and Queens; Harlem Success Academy is now part of the Success Academy Charter Schools network, of which Moskowitz—the author of a lively new memoir, The Education of Eva Moskowitz—is CEO. From that position, she has become one of the country’s most influential crusaders at a turning point for charter schooling.

The city Department of Education claims it can’t give Success Academy the middle-school space it needs because it’s just too hard to say if half-empty public schools will stay that way. That’s nonsense. Most of the buildings where Success wants to open new schools, in areas near its scholars’ primary schools, have had plenty of room for years, as the city’s own data show.

Last week, the City offered a “solution” to Success Academy’s rising fifth-grade families across Brooklyn and Queens: one building in East Flatbush. Success Academy has 12 elementary schools in Brooklyn alone: its middle school enrollment is set to triple in the next two years and in four years, Success will have 3000 Brooklyn middle schoolers. Mayor de Blasio’s non-solution means that scholars will be forced into a temporary, distant space, only to move yet again for seventh and eighth grades.

With rigor and joy as the guiding principles, Success Academy believes schools should be inspiring houses of learning where student engagement is the number one priority. With that in mind it has created a content-rich curriculum that is constantly being refined and improved. Because it is a charter school it has the autonomy to be nimble about making changes when something isn’t working for its scholars.

Fuming Success Academy parents blasted Mayor de Blasio Thursday for failing to provide adequate accommodations for the charter network’s burgeoning population of middle-schoolers.