I simply cut approximately four inch long pieces of duct tape, then split them in half to create thin strips. I wrapped them around each pencil near the eraser and secured the adhesive sides together. I trimmed the rough edges for a cleaner look, and finished up by writing each student's assigned number on the duct tape.
My plan is to have them show me their nub of a pencil when they need a new one as evidence that they've taken care of it. It's never too early to learn responsibility for their things!