I suspect that more than anything, the "good v. bad test taker" effect is an excuse, for students, parents, and bad teachers. But since I have collected and analyzed the data, from significant sample sizes semester after semester after semester, the burden of proof rests on the shoulders of anyone who claims that the "good v. bad test taker" effect is significant — particularly since no research exists to support it, one way or another.
He agrees that some people may be better test-takers than others (duh!), but that the effect is minimal. Here are some other points I think merit mention here (but you should go read the whole thing):
Think about it: Are some people better at certain types of tasks — like taking standardized tests — than others? Of course. However, I think the actual "good v. bad test taker" effect is exaggerated, and I have speculative, anecdotal, and empirical reasons to support my stance.
I suspect that if I had a magic wand and could wave it over my bad test taker student's head before he took the test, his score would not significantly improve, even though now, he is a good test taker.
The post merits a thorough reading.