I taught my first investing class 70 years ago. Since then, I have enjoyed working almost every year with students of all ages, finally “retiring” from that pursuit in 2018. 

Along the way, my toughest audience was my grandson’s fifth-grade class. The 11-year-olds were squirming in their seats and giving me blank stares until I mentioned Coca-Cola and its famous secret formula. Instantly, every hand went up, and I learned that “secrets” are catnip to kids. 

Teaching, like writing, has helped me develop and clarify my own thoughts. Charlie calls this phenomenon the orangutan effect: If you sit down with an orangutan and carefully explain to it one of your cherished ideas, you may leave behind a puzzled primate, but will yourself exit thinking more clearly.