"O Sacrament Most Holy" and an opening prayer and then asked them if they knew what the "Last Supper" was. Each class, from 1st to 8th grade, was able to answer that one.
Then I read Luke's account of the Last Supper and asked them to listen for words that we hear many times even when we're not reading the Gospel. They were able to immediately recognize those words--"This is my Body"--and to place them in the Mass.
I told them that when the priest says those words at Mass he isn't talking about himself; rather, Jesus is speaking those words through the priest and changing the bread and wine into his Body and Blood. Then with each class I went through something that St. Thomas Aquinas says: that when we come to the Holy Eucharist, the Blessed Sacrament, we can trust only one of our five senses.
Even the 1st graders knew the five senses. I asked: which of those five senses is the only one that St. Thomas says we can trust when we approach the Eucharist?
It took most of the classes a little thought and a few wrong answers, but eventually I was able to help them see that the one sense that can be trusted is our hearing. When we see, taste, touch, or smell the Eucharist it will appear to be bread and wine. Many Catholics and most other Christians rely on those senses and conclude that the Eucharist is a symbol for the Body and Blood of Christ. But relying on the sense of hearing, we believe differently. We hear the words "This is my Body ... This is my Blood" and we believe what we hear because Jesus said it. I think this teaching of St. Thomas Aquinas spoke across the intervening seven centuries to the hearts of the young Catholics with whom I met today.