More than half of the largest school districts in the country give parents a choice on where to send their children to school, a number that has doubled in the past 15 years.

Three districts received an A or A- in the newest annual edition of the Education Choice and Competition Index, published Thursday by the centrist Brookings Institution. Those districts were Denver, New York and the unique all-public charter Recovery School District in New Orleans, which scored best.

"There is much to learn from the efforts in New Orleans," according to Russ Whitehurst, the Brookings senior fellow who authored the report. "The Recovery District has a high availability of choice, with all of the public schools being charters. It also has a good supply of affordable private schools, vouchers for private school attendance available from the state and virtual education provided through the Louisiana Virtual School."

Districts score higher on the index for having a wide variety of public schools, including quality traditional schools, magnet schools, charter schools and virtual education, as well as affordable private schools. They also score higher if a large portion of funding follows a student to his or her school of choice, if it subsidizes poor families and if the choice process is simple for parents.

Since the last edition of the index, the districts that have improved most are Columbus, Ohio; Denver; San Antonio; Indianapolis; Osceola County, Fla., and Baltimore City.

At least in terms of school choice, the worst district in the nation is Alpine, Utah. Behind Alpine are Loudoun County, Va., and Camden, N.J.

"The lowest scoring district on the ECCI, Alpine, is a high performing district in Utah in terms of student test scores," Whitehurst said in a press release. "Alpine is a suburban district that overwhelming serves white, educated families. It may do a good job for its students, although empirically school districts don't have much impact on student test scores compared to the influence of family background and teachers."

Jason Russell is a commentary writer for the Washington Examiner.