Update: This article has been updated for context. A smaller percentage of students with disabilities enroll in Denver charter schools than traditional public schools — and that gap grows as students age.

But, according to a new report, the reasons for that gap and why it grows over time are much more complicated than the received wisdom that charters “counsel out” challenging students.

The report, which uses school choice data and school-level enrollment data from Denver Public Schools, was compiled by the Center on Reinventing Public Education, a Seattle-based research and policy analysis organization. The research was funded by the Walton Family Foundation.

In 2012, charter schools enrolled roughly 2 percent fewer students with disabilities in kindergarten, possibly because fewer of those students requested charter schools.

But the causes behind the growth in the gap — which nearly triples by eighth grade — are more complex. And researchers say that the typical narrative of “counseling out,” whereby charter schools encourage students with high needs to leave the school, may not be behind it.

At a panel announcing the release, Marcus Winters, the University of Colorado-Colorado Springs professor who is behind the report, listed a few potential contributing factors, including who applies to go to charter schools, who leaves them and how schools designate students as disabled. Winters is also a member of the Manhattan Institute, a conservative think tank.

His findings, which show low rates of students with disabilities leaving charter schools, are “really inconsistent with counseling out as a driving factor.” That’s not to say it doesn’t happen, Winters said, but it’s not big enough to be the driving force. In fact, students with disabilities are more likely to leave traditional public schools than charters.

Instead, Winters said that students without disabilities moving to charters — which lowers the proportion of disabled students — was a bigger force, contributing to roughly half the gap. The other half came from the fact that charters were less likely to identify previously unidentified students as needing extra support.

It’s an issue charter schools are grappling with, said Bill Kurtz, the head of Denver charter network DSST. He said schools often lower expectations for students with a disabilities designation but that schools have to find a balance between raising expectations and supporting students.

“What is the right bar to set?” Kurtz said, whose schools are known for a high-structure, high expectation model. “How do we think about accommodations?”

The full report is available here.

Note: The Walton Family Foundation is a contributor to Chalkbeat.