That is the headline of an excellent new op-ed from Eric Hanushek, one of the leading proponents of school reform. He makes a point that people sometimes miss: School reformers focus on teachers unions because they are an unambiguous impediment to reform. But it’s hard to focus your scorn on teachers unions without coming across as opposed to teachers of all stripes. Reformers like Hanushek don’t hate teachers. They dislike what the teachers unions are doing. As he puts it,

The typical teacher is both hard-working and effective. But if we could replace the bottom 5%-10% of teachers with an average teacher—not a superstar—we could dramatically improve student achievement. The U.S. could move from below average in international comparisons to near the top.

Teachers unions say they don’t want bad teachers in the classrooms, but then they assert that we can’t adequately judge teachers and they act to defend them all. Thus unions defend teachers in “rubber rooms”— where they are sent after being accused of improper behavior or found to be extraordinarily ineffective—on the grounds that due process rights require such treatment.

Bad teachers need to be removed from classrooms. This isn’t an anti-teacher stance: It’s common sense. But teachers unions are, by design, required to defend teachers good and bad. Hence their resistance to efforts to introduce objective evaluation standards: Without a way to judge people, they can argue that it’s impossible to tell who’s good and who’s bad, therefore no one should be fired. It’s an ingenious gambit in its own perverse way.