Wow, I had no idea. I could've done with some back when I was a teacher - the chalk we were given in South Africa in the 90's was squeaky, dusty and was too lig

Wow, I had no idea. I could've done with some back when I was a teacher - the chalk we were given in South Africa in the 90's was squeaky, dusty and was too light to fly true when you flicked it at an inattentive schoolboy