THIS IS MATH?

It is math time for the fifth-graders at Fernangeles Elementary School in Sun Valley, Calif., and everyone is stumped. The students have spent close to an hour puzzling over the question at hand: "What if everybody here had to shake hands with everyone else? How many handshakes would that take?" While the children, seated in small groups, debate and frown and scribble notes--and devise alternatives to the dread act of actually touching classmates of the opposite sex--their teacher, Kathy Pullman, roams the room. When the hour ends, no group has an answer. "This happens to be a particularly difficult lesson," Pullman...