Have you seen any of the threads on ceramic tiles? They are cheap, at least in the US, and require a low level of computer knowledge. While they are very easy technically, to do the very best ones requires a lot of artistic talent. Be warned that the sharpies many people use to color their tiles is not UV safe; they fade quickly if left in sunlight. Presumably you can spray the tile with a UV protectant. Here is a link to the main tile thread:
There are many ceramic tile threads, with some amazing work that I think would be perfect for you and your art students.