Tuesday, March 4, 2008

Class Size and the Achievement Gap

I hesitate to say this before having read the article (it's not out yet), but I think I figured out what's going on. This article in was published last Wednesday in EdWeek and describes a forthcoming journal article in which the author claims that smaller classes do not reduce achievement gaps. Meanwhile, another researcher who looked at the same data says that they do. I didn't have time to really think it through the first time I read it, but I think I see the difference now.

Both researchers look at data from the Tennessee STAR project, which is the only randomized trial of class size (students were randomly assigned to a class with either 13-17 or 22-26 students for a few years) and took place about 20 years ago. The author of this article, Spyros Konstantopoulos, says that the gap between the high and achievers was higher within small classes than it was in large classes. In other words, higher achieving students benefited more from smaller classes, so smaller class sizes do not impact achievement gaps.

Meanwhile, another researcher, Alan Kreuger, says that his research shows that lower-performing students and African-American students benefited more, and that, therefore, smaller classes reduce achievement gaps.

What? They're both looking at the same data. How can they reach different conclusions? Barring dishonesty or highly-technical formulas, here's what I think it is:

I think the answer is simple. In the newer article, he looks at the gap between the high and low achievers within each class, not the average score for each class. Meanwhile, the older study looks at the gap between the higher and lower performers across the sample. So the average score for lower performing classes could rise more than the average score for higher performing classes (many, if not most, classes are not extremely diverse -- they're within schools that are in wealthy suburbs or poor inner-city neighborhoods), meaning that the gap between high and low performing classes shrinks while the gap between the high and low performers within these classes actually increases. In other words, the lowest scoring students overall gained more than the highest performing students, but the highest-scoring kids within each class gained more than the lowest scoring kids within each class. So, in short, both of them are right.

If they're both right, to whom should we listen? Does reducing class size work or not? Well, you can argue it both ways. On the one hand, the society-wide "achievement gap" is really what we care about but, on the other, it seems that reducing class size doesn't reduce this in quite the way we'd anticipate. It seems that using the newest study to imply that smaller classes don't reduce the achievement gap is misleading, but that the way these changes affect distributions of achievement within classes offers food for thought. Of course, it would be nice to have a second study, one that's less than twenty years old, to compare to these findings.


Anonymous said...

I've had a long day after not much sleep, so could you clarify this for me. Doesn't it seem logical that higher achieving students would do better in large classes than lower achieving students?
Lower achieving students would need more personalized help. They are behind for various reasons, not the same reasons. Teachers need to deal with these various learning stumps. Also, for whatever reason, lower achieving students tend to be more obstreperous, and smaller classes tend to cut down the disruptions.
I teach students who are not on track to graduate, and our classes have grown from 17 to 25. This increase has substantially reduced our students' ability to progress. Yet, our administrators keep saying that research doesn't substantiate the need for smaller class sizes. But doesn't this research do just that?

Corey Bunje Bower said...

Yes, it does seem logical that lower achieving students would benefit more from smaller classes than would higher achieving students -- that's why the article caught my eye.

I haven't read the Konstantopoulos article, so I'm only taking an educated guess at what he finds, but I just read one of Krueger's old articles for class.

Krueger found that African-American students and those eligible for free lunch assigned to smaller classes made larger gains than Whites and those not eligible for free lunch. Based on that finding, it is fair to assume that the achievement gap across society would shrink -- the gap between rich/poor or black/white would be smaller.

As far as I can tell, Konstantopoulos found that, within a class the gap grows between high and low performing students. I don't know all the specifics but the two findings might not be contradictory. It's possible that the gap between the top and bottom performing students in a class could grow while the gap between the top and bottom performing students in society shrinks. This would happen if classes were fairly segregated so that many classes had top and bottom performers who were of the same race and income status.

I don't think anybody has examined the data from the Tennessee STAR experiment and concluded that class sizes didn't raise achievement. Whether research proves that small classes are needed depends on your prerogative and how much money there is. Students assigned to the smaller classes made significantly larger gains than those assigned to the normal size classes, but it's also quite expensive to have smaller classes. The question for a lot of people/districts boils down to whether smaller classes are cost efficient -- how much is this extra achievement worth and how much can you afford to/are you willing to pay?

Anonymous said...

Thanks for the clarification. I'm going to take the Tennessee Star experiment information to our administration. They say they make all decisions based on research and best practices. I'm curious to see their responses.