Jersey Jazzman seems to be in an endless battle with New Jersey’s largest newspaper, The Star-Ledger, or at least with the writer of its editorials. He went to the trouble of getting a doctorate in statistics so he could persuade that editorialist to understand how the charters produce high test scores. It is called creaming, picking the best and excluding the rest. 

This article explains how in works.

Creaming has become a central issue in the whole debate about the effectiveness of charters. A school “creams” when it enrolls students who are more likely to get higher scores on tests due to their personal characteristics and/or their backgrounds. The fact that Newark’s charter schools enroll, as a group, fewer students with special education needs — particularly high-cost needs — and many fewer students who are English language learners is an indication that creaming may be in play.

If you understand how creaming works (as in skimming the cream from the milk bottle when it rises to the top—a phenomenon unknown to people below a certain age), then the charter claims of superiority are unimpressive.

If you don’t understand, and you refuse to try, then you will find the Newark Test Scores to be “incredible,” as the Star-Ledger did. Parse that word: Incredible. Not credible.