I used to eat chalk when I was a child. It was the chalk we were writing on the blackboard in class. And so did most of my classmates. Almost every child I knew in my school, at least tasted it because they saw other kids eating it. Some liked the taste some didn't. It was difficult for our parents to convince us to stop, so all the parents were telling their kids that eating chalk would make them sick and get a high fever after eating it. So, some kids were afraid of doctors and injections and they were staying away from it. None of the kids I knew including myself took that habit into adulthood, but it's kinda funny we all did it as kids (in my neighborhood).