At The Quick and the Ed, Chad Aldeman disputes my assertion that Duncan’s impact on Chicago public school achievement was near zero. To make his case, Aldeman cites the fact that scores rose during Duncan’s tenure on 3 out of the 4 available NAEP tests. While true, this evidence actually supports my assertion rather than either Aldeman’s or Duncan’s.

Chicago’s gains on the NAEP tests ranged from 0.3 to 7.2 points on the 500 point scale, averaging out to a 1% increase in scale scores. I think 1% is pretty darn close to zero, and that’s what I said.

What’s more, as I wrote yesterday, the minuscule 1% improvement in Chicago NAEP scores was statistically identical to the improvement made by students in large central cities all over the country during the same period, so “The Duncan Effect” — his value-added over other large city superintendents — was precisely zero.

If there are other relevant data that I’m unaware of that paint a different picture, I’ll be happy to look at them. But the NAEP results flatly contradict Duncan’s own claims — routinely repeated in the media — that students made dramatic academic gains under his leadership.