You use three pieces of bread. You let all the kids see you put a piece of bread in a baggy with a…

You use three pieces of bread. You let all the kids see you put a piece of bread in a baggy with a glove on hence "controlled" then you wash your hands and put a piece of bread in a baggy for "clean" last but definitely not least you pass a piece of bread around and let every kid in class touch it then you put it in a baggy and label it dirty.

Watch how the bread changes over time due to germs. It is so cool and a great way to teach the importance of hand washing