I watched the blackboard rubber one once - the person concerned was looking round at a friend, chatting at the back. Teacher threw the rubber, person caught it. The catcher was the captain of the school cricket team..
I did stock up before I left for Whitby because you never know when you might want to pull a tooth out out or fish wish out of a drain hole or tie some across the bedroom door threshold to keep burglars out
Wind one end around the offending tooth bail out a bucket ,put the bucket on your head while standing in the road and before long you will have forgotten all about the tooth