Last year, my 8-year-old kids and their classmates designed and hand-built (eventually with dowels instead of screws) their own chairs at their amazing SF school. See http://www.sfbrightworks.org/2013/11/hawk-chairs/

Here's a quote about the lack of undo: "The consequences of careless work were immediate and unavoidable, and the amount of focus, resilience and perseverance required by these chairs was immense."