Along those lines, no modern educational reformer utters a single syllable about corporal punishment: doesn’t that make you suspect it’s effective?
Not really. I generally assume that experts in their field know more about it than I do, so the fact that they don't suggest it makes me suspect that it's less likely to be effective. This doesn't always work as an inferential method, but probably works more often than not.
Related: Son of Low Hanging Fruit
Another post on finding low hanging fruit from Gregory Cochran's and Henry Harpending's blog West Hunter.