Tom Levenson at Balloon Juice has a lengthy reply to my article on the value of good teachers that accuses me of neither understanding nor reading the paper at hand, and drawing incorrect conclusions from it. He’s wrong.

It’s ironic that Tom is accusing me of not reading a paper based on a blog post of mine that he has clearly not read, but has instead relied on the two paragraphs of it quoted by Conor Friedersdorf at The Daily Dish. Tom says I wouldn’t be as surprised by the results of the study if I were familiar with the literature:

That jolt would be a little less if you read—hell not the primary literature—but, say, just blog posts written by the New York Times’ best economics writer, David Leonhardt, who in the distant obscurity of … oh, this summer, reported on another study that looked at the impact of a good kindergarten teacher on future earnings and other social outcomes.

Anyone who is stunned by the specific result or the broader claim that educational outcomes have an impact on economic success simply hasn’t been paying attention…

Like Tom, I think it helps to put research in the context of existing literature, which is why I included this in my original post:

You can find similar results in the work of Raj Chetty, which suggests that good kindergarten teachers are worth $320,000.

If you follow that link you’ll see it takes you to that same David Leonhardt article, and had Tom actually read my post he would have seen this.

Unlike Tom, and despite having already read David Leonhardt, I do find Hanushek’s results “shocking”.  For one thing, Hanushek runs through a large range of plausible values for the parameters determining the value of better teachers and even with very large knowledge depreciation rates he still finds a value of $150,000 for a teacher in the 75th percentile with a class size of 20.

In addition, the net present value of over $100 trillion that would result from replacing the bottom replacing the worst 5-8% of teachers with average teachers would be, as Hanushek calls it, an “astounding” improvement in welfare. This is especially important given that, as Tom points out, we don’t yet have a good idea how to design performance pay in a way that ensures higher teacher quality. Hanushek argues that this difficulty raises the importance of the replace-the-worst-teachers policy:

The foregoing analysis has also implicitly suggested an alternative approach to simple performance pay that could be more cost effective.  If there is an accurate screen on teacher effectiveness, many of the properties of a performance pay scheme can be achieved by eliminating low performing teachers and paying the remaining teachers higher but relatively flat salaries.

So I’m sorry if Tom is not impressed or surprised by these results. Given the considerable media attention this paper has received, including bloggers at the New York Times, the Huffington Post, Education Next, the National Review, the Atlantic Wire, and the Daily Dish, I’m going to have to say that a lot of people disagree with Tom.

As an aside to all of this, I want to add that I don’t think those who prefer a system that consists mostly of public schools should be happy about the difficulty of finding good ways to structure performance pay and use value-added measures to identify effective teachers. The harder it is for social scientists to identify clear ways to improve the education system through bottom down reforms the more likely it becomes that more market based, bottom up reforms are both necessary and popularly demanded. I think this will mean things like vouchers, charters, and more creative reforms like this proposal Reihan Salam highlights from Rick Hess and Olivia Meeks:

Wisconsin would do well to start exploring a new model at the high school level. It ought to continue insisting that schools provide the 11 core credits, amounting to about 55% of the high school curriculum, but then rewrite the funding formula so that the per pupil allocation currently delivered to school districts is broken into two pieces: 55% to fund “core” mandated instruction and 45% deposited in a virtual Educational Spending Account (ESA) created for each child. Parents would have a choice. They could direct those ESA dollars to their child’s school and simply enroll their child in the usual manner, or they could use them to procure instruction from other state-approved providers.

If we could drastically improve the public school system simply through better pay structure and value-added measures then I think the public school system as it stands would require much less change than it’ll get if those relatively simple changes fail. I don’t think those who prefer a system that consists mostly of public schools will be happy with what we get when simpler reforms fail, because I believe the end result will be a more privatized system than would otherwise be necessary if we could centrally plan our way to a great education system.

For the record, I recognize that this is a very speculative claim, and there is a lot of room for reasonable disagreement here.