Tuesday, March 27, 2007

The Common School: A Question of Scale: Class-size Reduction and America's Misplaced Priorities

The Common School: A Question of Scale: Class-size Reduction and America's Misplaced Priorities

Via Eduwonk... new blogger "Dewey", who is reputed to be a minor education wonk, makes the case that class size reduction would have a tiny effect on educational outcomes.

But the really mind-blowing results come when you start comparing a class-size reduction to giving students a teacher with a reasonably good (though not unlikely) combination of teacher credentials (estimated by adding the relevant values in the table above). Clotfelter and Ladd do their own estimates of this sort and come up with a combined effect size of 15% - 20% SD for math (and 8%-12% for reading) of a well- credentialed teacher.

The first time I read this portion of the study I said to myself, "Yeah class size is less important,” but that finding is not particularly novel to anyone who follows this sort of research. But when I decided to actually compare how much less important class size is my jaw dropped. The effect size of teacher credentials is 8 to 10 times that of a major class size reduction in math and 6 to 8 times as big in reading!!!
He figures it would take approximately 150 billion dollars in increased salary costs (if the improvement for reducing students is linear that is), for a net benefit of 1.6% to 4% SD in math instruction. He then goes on to propose several novel ideas about how that money could be better spent for a much more significant educational outcome.

My only observation:

Isn't it possible that reducing class size would actually have a negative effect, instead of a small positive one?

We already have difficulty attracting teachers into teaching, especially in math and science. Doubling the number of teachers would have to entail reducing standards and quality.

Wouldn't the net effect of the lower average teacher quality more than cancel out the small benefits of reduced class size?

Go read the full post and if your statistically savvy, analyze his data and conclusions.

Pretty damn good for his 2nd post though.


rightwingprof said...

I skimmed the study, but that's it (sorry, but I don't think I should be reading academic writing on my birthday). I saw no serious problems with the methodology or the analysis, but I need to closely study their formulas for deriving some of their variables (though this study is the kind of thing that would have postmodernists running down the hall screaming after the first page if they had to read it). I don't agree with the critics that there was, as they put it, no control group. The authors are looking at the effects of several continuous, not discrete, variables.

But speaking of studies, hop over to my blog. I found one that was interesting.