I have a suggestion for Joel Klein, chancellor of New York City schools: Publish a teaching offenders list.

I must be a slow learner, because until Saturday I hadn’t understood New York City’s losing battle with the powerful teachers union. Once teachers achieve tenure—after 3 years—they are employed for life and damn near undismissible, even for cause. Journalism professor Samuel Freedman wrote about the situation for the New York Times two years ago: “Where Teachers Sit, Awaiting Their Fates.” I missed that one, but not Steven Brill’s shocking “The Rubber Room: The battle over New York City’s worst teachers” in Aug. 31, 2009, The New Yorker.