That’s the question FlowingData posed last week. Nathan Yau examined the average SAT scores and high school class sizes for every state, using a parallel coordinates plot. From his analysis, it looked like having smaller classes (fewer students per teacher) resulted in higher SAT scores. Makes sense, right? Fewer students means more attention from the teacher, which should result in better scores.

But this wasn’t the whole story. A lot of people commented on the original post, suggesting some other factors that weren’t being taken into account. The main effect was that of the ACT — because many states have students take the ACT rather than the SAT, these states have only a few students taking the SAT. In this case, the only students taking the SAT might be the ones who expect to do well (or those students applying to colleges which require it).

I’ve put up an interactive visualization of the education data by state, which you can use to explore the different relationships. One clear effect is that having a low percent of students taking the SAT does result in higher average SAT scores for that state. In the graph below, the y-axis shows the average composite SAT score for the state, while the color shows the percent of students who take the SAT. The highest scoring states all tend to have low percentages of students taking the SAT (the dots are more blue), while the states where more students take the SAT (the dots are more yellow) are on the lower part of the plot.

The question of class size and its effect on education is still open. The investigation is continuing on the FlowingData forums, where anyone can contribute their own visualization. I’ve put mine up there, but I’m looking forward to seeing what everyone else comes up with.

Here at Grockit, we’re interested in this topic because using study groups is one way students learn in Grockit.  Understanding the impact the size of a group has on learning helps us improve our learning environment.