Before a run a few weeks ago, I was retying my shoes and fiddling with my earbuds when I caught the tail end of a story on NPR. It featured a fourth-grade teacher in Miami named Marlem Diaz-Brown, whose students were interviewing her.
“What’s your favorite word?” one asked her.
She didn’t hesitate: “Kindness.”
“Next year,” she continued, “I’m thinking about taking all those classroom rules out and just writing down, ‘Be kind.’ ”