Eric Hanushek and Diane Racitch

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Ignoring Red Herrings

Ed Note – This week Eric Hanushek and Diane Ravitch are discussing whether removing the lowest-performing teachers is a good idea.  Hanushek started the debate on Monday and Ravitch responded yesterday.  Here’s Hanushek’s response below.   Ravitch will finish the conversation with a post tomorrow.

By Eric Hanushek

Diane comes back to a simple prescription:  We should pursue business as usual with a few extensions of current policy.  Unfortunately that is not serving us well, because this is exactly what we have done for several decades.  We have developed a system that pays little attention to students and their achievement but that supports any adult who has found a job in schools.  This policy does not look good by historical evidence on student outcomes.  But it is common to defend this basic lack of management by throwing in red herrings whenever any policy change is suggested.

Once more through the evidence:

We have clear and consistent estimates about the variation in teacher effectiveness that exists in schools.  The information comes from information on student test scores – something that is directly related to future student earnings and to the aggregate performance of the economy.

Differences in skills on tests of math, science, and reading lead to stunning differences in economic outcomes.   Economic outcomes are not everything.  But, as we have a continued national debate about both our international competitiveness and the fate of the bottom of the income distribution, we should not ignore economic outcomes.

Undoubtedly other, unmeasured things beyond test scores are also important to students and to society, but there is no reason to believe that being good in these other things is hurt by having greater measured skills.  And there is no reason to believe that teachers at the bottom in terms of producing measured skills are anything but the bottom in producing useful unmeasured skills.

It is a red herring to say there might be unmeasured other things that are also important.

Further, there is now consistent evidence that ratings by principals (on metrics other than test scores) are highly correlated with ratings on test scores at the top and bottom of the distributions.  While there is confusion in the middle, there is not confusion at the top and bottom.

It is a red herring to say that different evaluation systems produce different results.

If we put together the impact of good teachers on student achievement and the impact of achievement in the lifetime earnings of students, we find that a good teacher (one in the top quarter in terms of effectiveness) each yearproduces over $350,000 more income for her students compared to an average teacher.  But, symmetrically, a teacher in the bottom quarter subtracts $350,000 in income each year of teaching compared to an average teacher.

Ignoring these differences leads to huge inequities and to enormous waste in the potential of our students.  I personally think the stakes are large enough that we should consider something other than business as usual.