My students use pens. Not just sometimes, all the time. The only pencils in our classroom are colored pencils. Well, and the ones I use in my plan book because that can not be written in pen.
I made the switch to pens several years ago. I hated all the erasing my kids did, especially in their writing. I wanted to be able to see their thinking process as much as possible. Plus, elementary students tend to erase with vigor and often end up with holes in their paper. I also hated all the pencil sharpening. It's noisy and time consuming.
So I decided to get rid of pencils. The students don't even seem to notice a difference. They just draw a line through anything they want to change as they write and move on.
Pens do get lost and I have to replace them. But so did pencils. Occasionally students manage to take apart a pen but I try to see that as an experiment and exploration on their part. On the whole, I couldn't be happier with this decision.
The one thing I've learned, though, is to throw out the caps. They make awfully fun things to throw, chew on, bend, and who knows what else.
This idea has turned out to be brilliant, but I think it was really born out of laziness and irritation. I think that may be true of most of my good ideas.