A question about the history of the maths classroom (which I hope isn't off topic).
The idea of using a chalky stone to write graffiti diagrams on a dark plastered wall (marks that could be washed off and replaced) surely MUST have occurred early to ancient teachers of geometry in the academies. So much easier, you'd have thought, than drawing in the sand ....!
OK, so when do we first hear about something like blackboards??