In the middle of the night William, my five-year-old,\u00a0roused us from sleep thinking\u00a0that he\u2019d cracked his tooth\u00a0while\u00a0chewing on the zippered mouth of one of his stuffed animals. His father and I, abruptly\u202fawake, looked at each other in alarm\u00a0\u2013 sure that we were witnessing some kind of dental catastrophe. Except, of course, it wasn't a catastrophe at all. Late night Googling assured us that William was\u00a0only losing his first tooth, right on time and in a predictable location. When we told him his tooth would fall out soon and another\u00a0would\u00a0grow in its place,\u00a0he was shocked. The next day, having deposited both children at preschool, I was registering William for kindergarten. I walked through\u202fthe schoolyard teeming with children: children\u202fplaying tag, children climbing on a jungle gym, children whispering and shouting and laughing. Inside, as I handed over my umpteenth form, I mentioned our exciting loose-tooth\u202fsituation to the secretary. She sprang up. \u201cWait here,\u201d she said, \u201cI have something for you.\u201d She came back with a necklace, a slim\u202fblue\u202flanyard with a large white tooth charm\u00a0that opened.\u00a0\u201cWhen your son loses his tooth, he can carry it around in here,\u201d she said.\u202f\u201cThe kids wear it like a medal, even the fourth graders.\u201d That afternoon\u202fWilliam arrived home with his tooth taped to a paper.\u00a0His preschool teacher wrote,\u00a0\u201cWilliam was brave and calm when he lost his first tooth while biting into an apricot.\u201d I handed him the necklace. With\u00a0no instruction, William knew\u00a0that the tooth belonged inside. He slung\u202fthe necklace around his neck. He was\u00a0beaming,\u202fshowing his sister and racing through the backdoor. I read last week that in certain tribes in New Guinea\u202fwhen a boy loses his first tooth he leaves his mother's village and goes to live with the men. While my son won't be going so far\u202faway, there is the undeniable feeling of a leaving \u2013 through\u00a0the backdoor today, and onto the schoolyard tomorrow.