This is just great fun! Even my little boy could build and test bridges when he was 5. 6th formers would copy this onto a floppy disc (the old version used to fit) and take it home on their own initiative.
There are a variety of templates and competitions for the cheapest bridge are easy to hold as it tells you the price of materials on the screen. You can change the materials you use and the thickness of the beams. For older pupils there’s some information about the Young’s Modulus of the materials too.