In the 10 years since Hurricane Katrina battered New Orleans, there is almost nothing about the city that has changed more than its public schools.

In the months following the storm, the school system was swept away. The city’s 7,000 teachers were fired. The state took over almost all the schools and turned them into charters. Students were no longer assigned to schools via attendance boundaries; instead, they decided where they wanted to go and entered lotteries for a chance to enroll.

It has been an unprecedented experiment in urban school reform, closely watched by champions and critics as a sign of what policies might — and might not — work elsewhere.

By most measures, school quality and academic progress have improved in Katrina’s aftermath. But many community members feel that the city schools are worse off in ways that can’t be captured in data or graphs, arguing that parents have less voice than they once did and that the new system puts some of the neediest children at a disadvantage, especially those with disabilities or who are learning English as a second language.

And there is tension that centers as much on the way the reforms were instituted as on the reforms themselves. It was state officials, elected by the state’s white majority, who took over the schools from the local school board, elected by the city’s black majority. The teachers who were fired were mostly black; many of those teaching now are white, and they come from somewhere else.

“One thing after another makes it hard to swallow,” said Douglas N. Harris, an economist who heads up the Education Research Alliance for New Orleans at Tulane University. “It’s not hard to see why this is contentious.”

But Harris, whose group says it is dedicated to “objective, rigorous and useful research” to understand the city’s schools post-Katrina, also says that no other urban school system has seen student test scores (and graduation and college entry rates) rise as quickly as New Orleans’ in the past decade.

“We are not aware of any other districts that have made such large improvements in such a short time,” Harris wrote in a recent paper in the journal Education Next.

Below are seven data points that help explain how New Orleans schools have fared since Katrina. This is not an exhaustive list of the changes in the city’s public education since Katrina, but a sampling that shows how difficult it is to summarize the impacts of the city’s sweeping reforms.

1. In New Orleans, more than nine in 10 public school students attend charter schools, a far higher proportion than any other U.S. city.

In 2004, there were five charter schools serving about 2.5 percent of the public school students in the city. By 2014, more than 70 charters — each run by a separate independent governing board — served more than 40,000 students, or 91 percent of the city’s students.

No other city is even close, according to the National Alliance of Public Charter Schools:

2. Students traveled an average of 1.8 miles further to get to school in 2011-2012 than they did before Katrina, according to the Education Research Alliance of New Orleans.

One in four students attended a school more than five miles away from home.

3. Math and reading scores have risen faster in New Orleans than in other parishes affected by Katrina.

Before the storm, Orleans Parish public schools ranked second to last among Louisiana districts in math and reading test scores. Now New Orleans students are scoring at about the state average. Graduation rates and ACT scores are also up.

4. The city’s high school graduation rates are up sharply since before the storm, with 73 percent of students graduating on time in 2015, compared to 54 percent in 2004. The city was just two points shy of the state average in 2015.

The citywide average masks a huge, 28-point gap between the schools in the Recovery School District, the worst schools that were taken over by the state following Katrina, and the handful of traditional schools in Orleans Parish. But that gap has closed over time, and black and poor students in New Orleans are now graduating at rates higher than the state average for those groups, according to the New Orleans Times-Picayune.

5. Hundreds of thousands of people were displaced by Katrina and many — including many of the poorest — did not return, making it difficult to untangle how much of the test-score increase can be attributed to real educational improvements and how much is due to population change.

By 2010, the population of New Orleans had shrunk by 29 percent.

Harris, the economist at Tulane, estimates that no more than 10 percent of the test-score increase is attributable to population change.

6. In the new choice system in New Orleans, all students are supposed to have equal access to schools. But one-third of principals said that they cherry-pick students to improve their school performance as judged by test scores.

Those principals told researchers with the Education Research Alliance for New Orleans that they counseled out difficult kids, selectively recruited students likely to raise test scores or otherwise took steps to shape their student body, raising questions about whether the new New Orleans schools live up to their billing as a more equitable system for disadvantaged children.

7. Teacher turnover has nearly doubled since Katrina, largely the result of a new reliance on alternative programs with short-term commitments, like Teach for America.

The racial makeup of the teaching corps has shifted significantly, too. In 2003-2004, 72 percent of New Orleans teachers were black; a decade later, 49 percent were black.

In addition, the proportion of teachers with regular certification and with 20 or more years of experience has dropped significantly, according to Harris’s research. Given the simultaneous rise in student test scores, Harris suggests that this means that turnover is not necessarily bad. But many in the community say that the rapid turnover destabilizes schools.

8. The city is spending $1.8 billion, mostly from the federal government, to rebuild and refurbish the city’s school buildings.

Projects at 30 schools have been completed, according to the Louisiana Department of Education. Another 40 are in progress. Ten are yet to be undertaken.