I recently wrote an article that referred to charter schools that succeed by excluding students with disabilities, English learners, and others unlikely to get high scores. The editor questioned if this claim was accurate. I turned to several expert researchers to ask their view, and they all agreed with my assertion. David Berliner of Arizona State University—one of the nation’s pre-eminent researchers and statisticians—had data to back it up, and I invited him to write an essay addressing this issue.

He wrote:

Culling, Creaming, Skimming, Thinning: Things We Do to Herds and School Children

To cull is to select things you intend to reject, often in reference to a group of animals. An outbreak of hoof-and-mouth disease can cause authorities to order a cull of farm pigs. An outbreak of low-test scores or a meeting with undesirable parents can promote the culling of charter students. To cream is to remove…