Backers of the split, whose website is called Local Schools for Local Children, say the district has been failing for at least a dozen years, with some schools performing so poorly that the state took them over. In the 2011-2012 school year, six of 10 students attended a school ranked failing or almost failing by the state and the drop-out rate was 20 percent, according to Baton Rouge Area Chamber, a business group.

“Baton Rouge is one of the best job markets around, and the middle class is moving out,” said Republican state Senator Mack “Bodi” White. “Those who stay have their kids in private schools.”

About 30 percent of children within district lines were in private schools in 2009, according to Tulane University’s Cowen Institute for Public Education Initiatives.

White and other supporters say a split’s impact has been exaggerated, in part by estimates that assume a new district will pay nothing toward the current one’s retirement obligations, which they say they would share.

They also say an influx of state money would buoy the students and teachers left behind: “Nothing will happen to them,” said Lionel Rainey III, 36, a public-relations consultant who is the seceding group’s lead spokesman.

Poorer Still

James Richardson, director of the Public Administration Institute at LSU, who researched a split, said the remaining district will get more state dollars because it will have more impoverished children, but that won’t replace lost revenue.

The researchers assumed the new district would pay no retirement obligations because there has been no binding proposal for sharing them, he said.

Horacio Aldrete, a Dallas-based Standard & Poor’s managing director who studies school finance, warned of risk for both sides. A reduced tax base and declining enrollment could hurt the remaining district, while a smaller newcomer would lose efficiencies of scale as it hires superintendents and staff, he said. The splinter system may have to build schools and raise taxes if pupils migrate from private education, he said.

Baton Rouge is among several metropolitan areas where affluent enclaves threatened to secede.