Getting Nickels for Gravel

When Jesse was in first grade he got into the car after school all excited – look mom I made 15 cents. I asked him how he got the three nickels. He was all happy and said he sold some rock to the kids in his class then he showed me one of the rocks. Turning it over in my hands I saw it was gravel - like what covered the playground. I said, “Jesse this looks like gravel from the playground. Why did they pay you for it when they could just get for themselves during recess?” His answer made me laugh. He said, "They didn’t get it for themselves because they were too lazy."