Speaking of the positive impact of charters in other cities, here's an in-depth article in Politico about charters in DC:

But make no mistake: These almost Rockwell-esque scenes represent a genuine revolution, a triumph of a two-decade-long education reform experiment that has turned the nation's capital into ground zero for an ambitious overhaul of its failing schools. Thurgood Marshall—and dozens of other public charter schools that range across a wide variety of teaching styles and program themes—are the result.

It's a success that's seen in student lives: At Thurgood Marshall Academy, 100 percent of the school's graduates are accepted into college. And two-thirds of those students finish college, a rate that is higher than the national average—and about eight times the rate for D.C. students in general, says principal Alexandra Pardo.

Keep in mind that about a third of TMA's entering ninth-graders start off at or below a fifth-grade level of proficiency in math and reading, and come from 50 to 60 different middle schools across Washington, Pardo adds.

This, the academy's leaders explain, is charter schools done right.

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The nation's capital is perhaps an unlikely place for education reform to take such firm hold. Its school system had long been regarded as a failure; for years it served as Exhibit A for congressmen and U.S. Department of Education bureaucrats who pointed to their hometown as the poster child for underperforming schools. D.C. schools graduated just 48.8 percent of its students in 2006; only one in twenty students who started high school earned a college degree. Nearly a third of D.C. residents tested as functionally illiterate. Even as late as 2011, years into a massive reform push, D.C. still boasted the worst graduation rate in the country: 59 percent.

The city's schools were—and still are—deeply segregated. Many white parents sent children to local elementary schools and then pulled them out for high school, leaving many D.C. high schools overwhelmingly black and Hispanic.

Congress, in instituting the District's Charter School Reform Act of 1995, sought to remedy some of the deepest problems, but it wasn't until the election of Mayor Adrian Fenty in 2006 and the appointment of Michelle Rhee to lead the school system that the city really committed to reform. For many of the years in between, charter schools and a few limited-entry magnet schools, were the few shining lights in the city's education system; the reform efforts since 2006 have in many ways accelerated and compounded that growth and success.

…Charter schools have been seen as a way to give parents in low-income areas a choice in schooling much like what more affluent families have always had by moving into a better school district or putting their children in a private school. Instead of attending the school in their district, charter school students might go to school on the other side of the city.

D.C. today stands out because a whopping 44 percent of all its public school students—36,565 young people in 112 schools—are enrolled in charter schools, the highest state percentage in the nation. It's a number that has grown rapidly, increasing more than ten-fold since the 1998 school year. It's a figure that also stands out because D.C. charter school students consistently score higher on tests than those at traditional public schools in the capital.

…Ramona Edelin, executive director of the D.C. Association of Chartered Public Schools, a membership group for charter school administrators, says, "What's so powerful to me as an educator of 45 years is that some of these schools are having stunning success with the students that so many are concerned about. Students of color from impoverished backgrounds are doing dramatically better in charter schools in D.C. than they are in the traditional public school system."