An explosion of new charter schools in the last few years has turned Indianapolis into one the nation’s top cities for charter schools, a new study shows.

For the third year in a row, Indianapolis has landed among the top ten cities on the National Alliance For Public Charter Schools’ annual ranking of charter school capitals. The measure ranks cities by the percentage of students enrolled in charters.

With 31 percent of the city’s public school students, or 13,830 kids, enrolled in charter schools in 2014-15, Indianapolis ranked ninth on this year’s list.

New Orleans has been No. 1 since the city’s education system was reshaped by Hurricane Katrina. Last year, 93 percent of students in that city attended charter schools. The other cities in the top five are Detroit (53 percent); Flint, Mich. (47 percent); Washington, D.C. (44 percent); and Kansas City (41 percent).

Also in the top ten is another Indiana school district, Gary, which ranked sixth with 40 percent of public school students enrolled in charter schools.

Charter schools in Indiana have surged in the wake of a 2011 state law that expanded the number of organizations that could grant new charters.

Previously, the mayor of Indianapolis and Ball State University were the state’s only major charter schools sponsors. Now, schools can be sponsored by the state charter board or any private university.

That’s led to a 76% increase in the number of charters statewide, from 49 in 2011 to 86 this year. That increase is despite the handful of schools that were closed for poor performance.

Last year alone, 14 new charter schools were approved statewide.

Several cities in the top 10 are adding new charter schools quickly. As a result Indianapolis has actually slipped in the rankings to ninth from eighth last year. But its charter school percentage is climbing, and all signs suggest those numbers will accelerate in the next few years.

Indianapolis first appeared in the charter school rankings in 2008-09 at No. 13 but its numbers six years ago were much smaller than today: About 7,500 charter school students amounted to about 18 percent of the city’s public school students that year.

The number of charter school students has nearly doubled since then.

Some of the increase is attributable to Indianapolis Mayor Greg Ballard, who has expanded the number of charters sponsored by his office.

In 2011, the mayor’s office sponsored 18 charter schools. This year it sponsored 33 schools, including six new schools that opened this year. Three other new charter schools opened in the city this year, sponsored by the Indiana State Charter School Board.

Ballard, a Republican who has decided not to run for re-election, leaves office in January. His replacement, Democrat Joe Hogsett, has said he doesn’t expect to make big changes to the way the mayor’s office approaches charter schools but says he plans to enforce tougher consequences for charters that fail to meet their goals.