[alawton]

That is a large class! I bet it is loud. When I have taught larger groups of kids and I did activities I usually split them into groups of fives. The activity would be one in which the groups need to keep their answers secret while they are working on them. Have each group describe five of the vocabulary words without actually giving the word away. The groups have to present the clues to the entire class for the other students to guess. While working on the clues each group will try to keep things quiet so other students won't know which words they have picked before it is time to present. If your kids are competitive they won't want to give away their answers. Good luck!