I'm wondering how other art teachers deal with using tempera paint and reducing the waste involved. I have the students use Styrofoam plates as pallets, and then they wash off their plates, but often there is a lot of paint going down the sink. I encourage them to take only a small amount of paint, and many of them are doing a good job with it, but I still feel like there is a lot of waste. We've tried saving the paint from one period to the next, but most students want to start with a clean pallet which is understandable. I teach high school and have 4 periods a day of painting. Any advice?