November 2, 2009 12:36PM

The Bell Curve Mean Business

Over the past month, Charles Murray and I have been debating the proposition that better schools can significantly improve educational outcomes – can shift the “Bell Curve” substantially to the right. Charles finds this “touchingly naïve,” while I argue that it is empirically inescapable.

Ben Chavis, founding principal of Oakland’s extremely high scoring American Indian Public Charter Schools, has invited Charles to put his skepticism to the test, and perform research to validate or refute the achievements of Ben’s inner‐​city students. But Charles believes he’d find only a modest (< 0.25 std. dev.) test score effect to AIPCS attendance, that would, moreover, be evanescent. Charles grants that Ben has created a very good school, he’s just convinced that even very good schools cannot have large or lasting academic effects.

The evidence simply does not support Charles’ skepticism.

I’ve already noted that there are average effect sizes for market education systems that are much greater than Charles’ threshold. Just a few months ago, it was reported that three years in private schools under DC’s voucher program raises reading achievement by two grade levels (0.42 std. dev.), and effect sizes of even 2/​3ds of a std. dev. are not unheard of.

Those are average effect sizes of competitive education markets over public school monopolies. Since we agree that Ben’s school is quite special, there is every reason to expect his school’s effect size to be on the high end of the range already identified in the research.

And what of Charles’ assumption that school effects are necessarily evanescent, fading to insignificance within a few years after students leave the school? This, too, is contradicted by the evidence. Numerous studies have looked at long term effects of consuming market schooling instead of monopoly schooling – particularly on students’ eventual success in college and their earnings once they’ve entered the labor market. Economist Derek Neal has found that urban blacks attending Catholic schools are twice as likely to graduate from college as similar students attending public schools. That is a large effect several years out, and it, in turn, will have an enduring positive effect on students earnings. In fact, of 17 research findings comparing the eventual educational attainment and earnings of market school graduates to public school graduates, 11 find statistically significant positive effects, and none find significant negative effects (see Table 3 in the previously linked paper).

The evidence is clear that competitive education markets have significant, lasting, and often quite substantial positive effects over government school monopolies. So I can see no empirical basis for Charles’ skepticism.

What’s more, this should be intuitively obvious. The current mean of the bell curve of educational achievement is not some inescapable fact of nature, like the value of pi. It is a symptom of the monopoly school systems that have stifled educational efficiency and innovation for more than a century. Just as establishing the rule of law and liberating economies from the thrall of central planning have led to dramatic economic growth around the world, so would liberating education from the thrall of government school monopolies shift the bell curve to the right.