Many theories have been proposed. Some people think that boys are hard-wired so that they learn more slowly, perhaps because they evolved to fight off wolves more than to raise their hands in classrooms. But that doesn’t explain why boys have been sinking in recent decades.

Mr. Whitmire argues that the basic problem is an increased emphasis on verbal skills, often taught in sedate ways that bore boys. “The world has gotten more verbal,” he writes. “Boys haven’t.”

The upshot, he writes, is that boys get frustrated, act out, and learn to dislike school. “Poor reading skills snowball through the grades,” he writes. “By fifth grade, a child at the bottom of the class reads only about 60,000 words a year in and out of school, compared to a child in the middle of the class who reads about 800,000 words a year.”

Some educators say that one remedy may be to encourage lowbrow, adventure or even gross-out books that disproportionately appeal to boys. (I confess that I was a huge fan of the Hardy Boys, and then used them to entice my own kids into becoming avid readers as well.)