“When you’ve got high stakes on something, if there’s a way to corrupt it, some people are going to corrupt it,” said Diane Whitmore Schanzenbach, an education researcher at Northwestern who wrote a brief highlighting the advantages of using chronic absenteeism to measure schools. “The question is, how big is this incentive? How many schools are going to engage in this bad behavior?”

A 2003 study in Chicago found evidence of cheating on standardized tests in about 5 percent of elementary classrooms. More subtle gaming has also occured: research found evidence that teachers focused on topics likely to appear on the state test, at the expense of other academic standards.

The potential problem may be more acute when it comes to student absences because of the all-or-nothing way chronic absenteeism is measured.

In most states, a student is deemed chronically absent if they miss 10 percent of school days—around 18 days for those enrolled for a full school year. That means that schools might be especially tempted to mark a student present on the day of their 18th absence. (If student-attendance rates are bunched right below the chronic absenteeism bar—say, many more are gone 17 rather than 18 days—that could be evidence of manipulation.)

“We need to use accountability to promote an early-warning approach — not just making sure kids are one less day absent,” said Hedy Chang, the executive director of Attendance Works, a nonprofit that promotes efforts to improve school attendance.

Both Jordan and Schanzenbach noted that, because states are generally counting chronic absenteeism for only about 5 to 10 percent of school ratings, the incentives to cheat are likely to be fewer.

“It’s going be an empirical question about how big is the corruption of this—my prediction is it’s going to be reasonably small,” said Schanzenbach.

“This is why we encourage people to keep chronic absence to a relatively low percentage of the overall weighting—if it’s less than 10 percent … it’s not worth investing in trying to game it,” said Chang.

Still, attendance manipulation scandals have cropped up before: A 2016 investigation in Chicago, where student attendance rates are a part of school scores and principal evaluations, found that four high schools had systematically changed attendance records.

Others are concerned about data issues beyond obvious cheating.

“I’m worried about outright manipulation, but I’m also worried about sloppiness of reporting and inconsistencies,” said Chad Aldeman of Bellwether Education Partners, a reform-oriented consulting firm that has undertaken an extensive review of state ESSA plans. Details like how schools count partial-day absences, or what happens when a teacher forgets to take attendance, will take on new importance.

Experts agree that there should be some protections against manipulation of attendance data. But it’s unclear to what extent states have those safeguards in place.