Naturally, we must discuss the construction of the board itself. There are two aspects to the board- the grid itself and the connections behind the board.
Thus far, our resident board expert Jude has made two different board surfaces. The one on the left above was a piece of pegboard- we taped off some lines before painting it to provide visible demarcation between the halves of the board and the vertical columns down the side. The one on the right was far more labor intensive- Jude made a pattern from some pegboard and used it as a template to drill holes in a piece of whiteboard. That allows the instructor to make notes about the circuit easily.
The connections on the back side of the board have been the subject of much experimentation. The problem is simple- the conductive element must be cheap, easy to work, and durable. Durability ruled out aluminum foil. Cheapness ruled out copper foil. Easy to work ruled out steel sheet.
In the end, we found two methods that work, both involving the same insulating foam we used for other applications throughout the process, and both requiring a channel to be cut in the foam. The top piece in the picture above was the quick and dirty method- stuff the channel with steel wool. It works great, but it has a major flaw in the fact that a short circuit through the steel wool could easily cause the bundle of steel wool to catch fire, and the foam and wood construction of the rest of the piece is hardly fireproof.
The bottom piece was ultimately selected as the best-in-show- it's a folded piece of beverage can that has been slightly roughed with sand paper to expose bare metal. Over time, there may be some issues with oxide forming and preventing a good connection, but that's not likely to be a long term issue.
A final, equally valid solution: skip the busing entirely and make a discrete connection on the back of the board using alligator clips and wire, or any other desired method. This trades up front work for work before each class but it could be worth it if the methods presented here prove to be long-term reliability killers.
Also, note that there is nothing saying these solutions are the best- only that they are the ones we came up with after some trial and error.