When Raj Chetty and his colleagues identified the extraordinary contributions an excellent teacher can make to a student’s lifetime earnings, a number of outlets, including the New York Times, drew attention to the findings, which many saw as a slam-dunk case for higher teacher pay. Yet the researchers also find that a substandard teacher can cause a comparable amount of economic damage, thus suggesting that tenure policies that protect such teachers are potentially very costly in terms of their long-term impact. Paul Peterson describes the ensuing controversy in a short post.