When my students borrow a pencil or pen, I make them leave me a shoe in exchange. It's pretty hard to forget your shoes, although just yesterday one of my students did just that.
On Tuesday I gave out tests to the poor little darlings. I didn't require a shoe that day. It seems a bit cruel to make a child take a test without one of their shoes.
I lost more pencils and pens that day than I did in the whole seven weeks preceding it.