[ August 30, 2006: Message edited by: Slartibartfast ]
I'm doing applied calculus this semester. The first room didn't have an eraser, so I used a piece of paper... the second room had a giant splotch across the center board that I couldn't erase or write over. The students were fine. I now have my own eraser. I always bring my own markers, but I've never had an eraser shortage before.