Stump the Teacher Day

One of my students tried to stump me on a question. He asked what glass is made of. When I answered sand, he said, "Crap." Quickly I answered, "No, just sand." He didn't get it for a minute, but then grinned and said, "Then it would be yellow glass, and we wouldn't want that." Meanwhile the rest of the class is oblivious to what was said. That's what makes it so much fun this year, having a student who gets my quick-wit and returns it as well.