Here's a great way to recycle and put responsibility on the students for making up absent work. I highlight the names of my students on the daily absentee sheet we receive in the morning. In the blank area at the top, I list what we did that day (it matches what I put up for students to copy into their agendas), and if there are any worksheets for the day, the lab partner puts the absent student's name on the top and places it behind the sheet. The sheets are placed in a notebook. Each new day's sheet goes on top, so the current date is what they open the notebook and see. Students know they are responsible for checking this notebook at the front of the room and turning the make-up work in within the allowed time. If any students ask me what they need to make up, I just tell them to check the notebook. It's amazing how many times they think they turned in work, to end up finding their name on a sheet in the make-up work notebook!