Just a random teaching tip...
When I first began teaching I was always afraid that I would give a student my original worksheet by accident and lose the worksheet forever! I kept extra "back up" copies of everything until my filing cabinet was ready to bust but then I discovered this handy little tip. I use a yellow highlighter & write "original" on MY original copy. When the worksheet is copied the highlighter does not show up! How awesome it that?!?! This makes it so much easier to keep my original copies safe and sound! It also helps my parent volunteers keep the originals separated when they are making copies for me. ALWAYS test the highlighter brands in a small area first because some of the cheaper brands will show up a little bit when copied. Yellow seems to be best but some of the other highlighter colors work as well.