Two scholars demonstrated what we already knew: many charter schools are skimming and choosing the students they want while excluding the ones they don’t want, the ones likely to cost too much or pull down their test scores.

Peter Bergman and Isaac McFarlin Jr. tested the hypothesis.

Here is the abstract of their paper.

School choice may allow schools to “cream skim” students perceived as easier to educate. To test this, we sent emails from fictitious parents to 6,452 schools in 29 states and Washington, D.C. The fictitious parent asked whether any student is eligible to apply to the school and how to apply. Each email signaled a randomly assigned attribute of the child. We find that schools are less likely to respond to inquiries from students with poor behavior, low achievement, or a special need. Lower response rates to students with a potentially significant special need are driven by…