The kids started off by defining length without using the word "long". They then built paper boxes of varying shapes and sizes to determine the most efficient width * height * length configuration to hold sand is. They then figured out the relationship between surface area, volume and mass. They modeled their boxes in an online applet. The kids learned about the "zero axis". They then modeled a beam using an applet that gave information about the structural integrity of a beam. They tested various sizes of beams for strength within the apple then tested it in real-world models.