As part of the ongoing paper engineering series and as a follow-up to the posts on paper platforms and paper chains, here's a suggestion for another design and construction project.
The objective is to build a center-load-bearing bridge between two platforms with fifty sheets of paper and a roll of tape, either optimizing weight supported with the condition that the platforms be at least two feet apart or optimizing distance between platforms with the condition that the bridge most support at least five pounds. You might also want to try a variant where a long piece of string is included allowing for suspension designs.
Like the platform project, this is one of those assignments that increases in complexity as the students advance. You can give the same instructions to a fourth grade class and to a group of freshman engineers with equally challenging results. You could even make this an annual event and watch the designs grow more complex and the approaches more sophisticated as the years passed.