I came across this cup-stacking activity from Jaclyn Sepp when I was looking for some ways to help the students work on teamwork. I did it with 5 different classes of 8th grade students with various levels of success. (Note to self – don’t have the cups on the table while you are trying to give directions.) I found that it definitely works better with at least 5 students in a group, and that they love making challenges for other groups once they have completed the first two! (Link at the bottom of her post will take you to the second challenge.)
