Test Results and Drive-By Evaluations

Isn’t there a better way to judge teachers?

By Thomas Toch

New York City Schools Chancellor Joel I. Klein wants to rate teachers in the nation’s largest school system on the basis of their students’ test scores. It’s a radical idea in public education (where teachers’ credentials have always mattered more than their performance), and the stakes are high: The nation spends $400 billion a year on public school teachers’ salaries and benefits.

Klein and his deputy, Christopher Cerf, see a clear logic in giving student test scores a role in teacher evaluations: It’s inexpensive and easy to administer and seemingly measures what matters most—student achievement. The vast majority of public school teachers are paid strictly on the basis of their seniority and the number of college credits they’ve racked up, rather than for their performance in the classroom, and Klein and Cerf want to change that, and rightly so.

But standardized-test scores aren’t the simple solution they seem to be. For one thing, only about half of public school teachers teach the subjects, or at the grade levels where students are tested, eliminating the prospect of a system that’s applied...