On an unseasonably cold day last November in Foley, Ala., Colby Royster and Michael Peterson, two students in William Bender's fourth-grade public-school class, informed me that the class corn snake could eat a rat faster than the class boa constrictor. Bender teaches 26 fourth graders, all boys. Down the hall and around the corner, Michelle Gay teaches 26 fourth-grade girls. The boys like being on their own, they say, because girls don't appreciate their jokes and think boys are too messy, and are also scared of snakes.