Racer, if you took the best of three bad guitars with you to a class you can let kids, particularily young and exuberant kids - like Mbo for instance -, feel it and touch it and even get SOME sound out of it. You can explain that it is not a great guitar and that there are problems with it, but it might be useful for showing what a guitar feels like on the lap and under the fingers. Alternatively they might be useful as models of what a guitar looks like inside if you cut away one side of one.