Why I don't allow erasers in my classes

Well, not in my younger classes anyway. Kids here in Korea, like in most places I'm sure, always have beautiful school supplies. I suspect that this is where they learn that having nice pencil cases means learning a lot or well. This is, naturally, a really lousy thing to learn.
I've got a new student who started in my first grader class yesterday. He's a real prissy momma's boy: his mother has waited the full hour class right outside the door the last two days with his baby brother in tow. We just got done with our phonics books. At one point he said "Mr. Mondello, can I have an eraser please?" and I said "No, we don't use erasers in our phonics books, just cross out your mistake and write next to it. He kind of froze, it looked like a mental paper jam, and he just asked again, in the exact same tone of voice, "Mr. Mondello, can I have an eraser please?" It's been a class rule for so long I'd almost forgotten why they weren't allowed, but my students hadn't. They all chimed in "It's OK, write under [the mistake in the margin]" and "Make a mistake is no problem, forget it."
These kids with their perfect little pencil cases and immaculate erasers are generally speaking terrified to make mistakes, which, generally speaking, means they never take risks. As a language teacher, the number one job is to break that fear of being wrong.
But that's not the only reason to hate erasers. When I was a first grader I remember my teacher specifically banning erasers from the classroom. I asked my mom and she conjectured that I teacher wanted to see our mistakes. I know think I know the true reason, and my ulterior motive for banning the use of erasers: not only are erasers incredibly distracting and give students a great way to waste time, they also make a big mess. The Korean name for that oh-so messy eraser dander: jiugeddong (지우개똥), literally 'eraser shit'.