As discussed in previous sections, education research suggests that academic ability and verbal ability (and perhaps advanced degrees in math and science) are typical of effective teachers. Certification, extensive pedagogical training, master’s degrees in education and experience after the first few years are inconsistent indicators at best. Clearly, these findings suggest that many of the incentive structures that motivate teachers to seek certain credentials and that encourage individuals to stay in the profession regardless of their classroom performance are misaligned. But does this mean that we should simply modify those practices to favor teachers with higher academic and verbal ability?

Probably not. While there may be some basis for thinking of such direct reforms, we must always remember the potential for a reform to have unintended consequences. As Goldhaber’s research in North Carolina suggested (see Part III), raising cut scores on teacher exams — one sign of a teacher’s academic ability — can quickly start to exclude effective teachers. Moreover, we must remember that correlation is not causation. A high IQ does not always help a teacher be more effective in the classroom. After all, a particle physicist may struggle to explain elementary mechanics to students. By defining teacher quality in terms of growth in student achievement — the ultimate goal of policy reform — policymakers can focus on retaining and rewarding the teachers who help students succeed, not on teachers who only might be more effective.