What I learned from doing this was to plan out what jobs need to be done ahead of time -- not just in your head, but write down a list, with time equivalents for each job, so that you can assign them without much thought. The first time I had a clean-up day, I was rushed with students enthusiastic to work -- it was much easier the next time when I made a list.
Several jobs can be accomplished, from washing glassware or returning equipment to lab drawers to decorating the classroom or creating new displays! Your students will be very enthusiastic about this credit earning opportunity.
I had a "Class Participation" grade for my students each quarter -- it was mainly based on attendance and tardiness. This extra credit opportunity would earn points towards that grade. I categorized it as a "Homework" grade, and with this extra credit students could have a Class Participation grade of over 100 points. You'll have to decide how you want to award this credit, but it was equivalent to a Homework grade (not as high of a value as a Test or Lab grade). I may be talking about computer grade programs later this summer.
I'd love to hear about your Lab Clean-up experiences! There should be a "Contact" form below, or click on the "Contact" tab on the top right of this page.
Check out my lab book "Chemistry on a Budget" at amazon.com -- it's only $20!
Each lab is presented with two possible report formats -- both labs use the same procedure but each has a different conclusion -- one with 10 questions to be answered as a conclusion, the other with a full laboratory report required. This gives the teacher the option of what type of report is desired, and each version is designed to be just two pages. This way the teacher can photocopy just one 2-sided page per student (saves paper).
Have a good week!