Chewing on Pencils

With school approaching I have found that we HAVE to use pens for my son. It's not really an option. My son tends to chew the pencil tops (below the metal if it has it) to the point he breaks the top off. I have noticed with pens this is harder. I know as he learns to write he will need a pencil of some sort. My solution was to take rubber tubing you can find at a medical supply store, spots store or even then some fishing store tubing to put on the top of the pencil to allow them the ability to chew as needed without breaking their pencils constantly or chewing off the erasers. I have noticed him doing this with pens too but they tend to be harder to break and he doesn't have to worry about them being sharpened either... just another task. I would suggest mechanical pencils EXCEPT then he'd be playing with the part that makes the lead come out. Maybe when he's a little bit older.