The kids did pretty well guessing close to the number of jelly beans in each of their jars. As for a class assignment I think it was a lot of fun and helped them make a big connection to the word, "estimate." The fall back was that many students were disappointed they didn't win. I suppose I could have given out the jelly beans evenly to the class and let the winner just feel good. But I sometimes feel that things can't always be "even" for these kids.
A lot of emphasis in Elementary school (especially the younger ones) seems to be that everything has to be the same and fair. I explained the rules before they put in their numbers and so they should have understood. What was good, I think, was that some classes had a group of all the same close numbers. So I let them play rock, scissors, paper to sort it out.
One of the winners came up to me the day after, and told me that her dad had eaten all the jelly beans. I thought that was pretty funny and cute. If you are thinking of doing this for a math lesson or just for fun I highly recommend it. You can have them write sentences or make up a story, who knows!?