Part of the rationale behind the charter school movement, which took off in New Orleans after Hurricane Katrina, was to cut the cost of school systems' large central bureaucracy and spend more dollars in the classroom. 

But while the city's public schools have improved by most measures in the years since then, a study out Tuesday finds that under the new regime, more money actually gets spent on administration, and less in the classroom, in Orleans Parish than in traditional school districts.

It's the result mainly of a drop in teacher salaries and benefits, which tend to lag behind the pay of educators in traditional districts across the state. However, researchers noted that New Orleans teachers also have less experience on average, and that charters are exempted from the state’s pension system and are likely to have cheaper retirement plans.

Meanwhile, the upswing in administrative costs is in large part due to higher total pay for administrators. That includes a rise in salaries for school leaders and, to a lesser extent, a rise in the number of people on school administrative teams.

“The fact that instructional spending has decreased despite a large increase in operating expenditures is striking,” said Douglas Harris of Tulane University's Education Research Alliance for New Orleans, the group behind the report.

The research compares public school spending in New Orleans with that of 17 other school districts in Louisiana over a 14-year period. It accounts for the increased costs charter schools spend on transportation in a system that caters to parent choice, as well as the money given to outside consultants that provide services for the independent schools.

It further notes that New Orleans spends more on public education now than it did before the storm, and that new teachers still earn more today than they did back then.

The report is likely to reinvigorate criticism that charter schools churn through large groups of low-paid rookie teachers so that their CEOs can collect big checks, though Harris and his colleague Christian Buerger point out that charters are also more likely to hire administrators with degrees from top-ranked colleges or with backgrounds in business, who may be able to command higher salaries.

Charters might also need more administrators to guide their relatively young teaching staffs, the report noted, and smaller charter managers don’t benefit from the economies of scale that large school districts do.

In any case, the authors said the decline of teacher experience and rise of management costs don’t appear to have negatively affected students' performance. But they questioned whether the model can be kept up indefinitely.

“There are signs that interest in New Orleans is abating among younger teachers, and growing concern about the constant churn of teachers who do not plan to stay or make teaching a career here,” the authors wrote.

Given state budget woes, cutbacks to education funding are another possibility. The state might also force charter schools to pay into the state retirement program in the future, the study noted.

Follow Jessica Williams on Twitter, @jwilliamsNOLA​.