...But try, if you can, to strip away the haze of nostalgia and sentiment through which we generally perceive Mark Twain's world, and imagine how a boy like Tom Sawyer would be regarded today. As far as I can tell, that fight is not just "inappropriate behavior," to use current playground terminology, but is also one of the many symptoms of "oppositional defiant disorder" (ODD), a condition that Tom manifests throughout the book. And Tom is not merely ODD: He clearly has attention deficit hyperactivity disorder (ADHD) as well, judging by his inability to concentrate in school.... I am not...