We used another middle school class period for still life painting.
I brought in several fruits and several bags of chips and soda cans that used the same colors as the selected fruit. The students aranged them on the table (very well I might add) and painted them as they saw them.
Throughout this class period we talked about the difference in the two groups of food. We talked about colors, nutrition, space, and composition. Before they left the students begged me to sell them the chips and pop. I gave them their choice of what to take for free and in the end, took the fruit home. It's a work in progress.