Break them into 2 teams. Have 1 team go outside next to a straight exterior wall of a building. It has to be out of sight of the other team. Give them a piece of paper with tape on one side. They have to get the paper attached to the wall as high as possible.
While they are doing that, the other team can be having a snack, playing quieter games, etc.
Trade. Have the 2nd team try to beat the height of the first team. It's a great way to get them using engineering concepts while being physical. After both teams have done it and you have a winner, have each team share their strategy. Hopefully they can discuss why the winning team's solution was better.
