Already a lightning rod in the city’s mayoral race, charter school enrollment patterns are getting renewed scrutiny at the state level.

Chancellor Merryl Tisch and her colleagues on the Board of Regents have asked state education officials for months to increase transparency around student attrition data for charter schools. At June’s Board of Regents meeting, Tisch echoed concerns from critics who charge that some charter schools prop up their test scores by encouraging high-need students to enroll elsewhere.

“I would make a list of charter schools that have ushered out 5 [or] 10 percent of their kids in the first six [or] seven weeks,” Tisch said. “Make a list of the ones who are ushering them out right before testing.”

Now, state education officials have announced that they are developing a way to spotlight exactly that issue. A proposed “stability index” would use  regularly reported enrollment data to flag suspicious trends, such as high discharge rates at the beginning of the year or right before state testing at the end of the year.

The proposed index would include all schools. But officials said last month that they would especially monitor the enrollment of charter schools, which are required under the 2010 charter schools law to serve students with high needs at rates ”comparable” to their surrounding district. Enforcement has so far been lax, but starting next year, charter school authorizers will factor enrollment into decisions about whether schools can continue to operate.

Tisch signaled that she wanted to see the stability index made public with a ranked list of charter schools with the most suspicious student mobility data.

“The way we hold other schools accountable for a variety of things we’ve never held [charter schools] accountability [for],” Tisch added. “A public list, I think, would be a way of starting to design an accountability system.”

Tisch’s comments largely mimic the positions laid out in the education platform for Bill Thompson, whom she is supporting in the city’s mayoral race. In his lone education speech during the campaign, Thompson said charter schools should be held “to the same standards as public schools.”

State Education Department Assistant Commissioner Ken Slentz warned against drawing conclusions purely from student mobility data. He said the state would investigate schools that showed particularly high mobility, but that no definitive intervention could be taken based solely on what is found on the index.

A persistent criticism of charter schools, which accept students through an application lottery, has been that they do not serve an equal number of high-need students compared to local district schools, an assessment that was largely validated for the city’s sector last year in a report by the New York City Charter Center. For instance, 80 percent of charter schools have fewer poor students than their district average, the report found.

Some charter school advocates have criticized state efforts to monitor and mandate enrollment patterns. But Charter Center CEO James Merriman said the charter sector welcomed opportunities to share its enrollment data.

“If the Regents are proposing additional transparency in how all public schools enroll and retain students, we’re all for such measures,” Merriman said in an email. “Charters have nothing to hide.”