K12Net
A FidoNet-based network for schools from around 1990, where teachers and pupils held discussions long before classrooms had internet access.
Schools in the early 1990s rarely had a direct internet connection, but a PC with a modem and a BBS was within reach. K12Net was built on FidoNet technology: echomail conferences for different subjects and age groups, exchanged overnight between school BBSes. The name refers to American schooling from kindergarten to twelfth grade.
The conferences were gated onto Usenet as the k12.* hierarchy, so universities and internet-connected schools could join in. It was an early case of classrooms writing to classrooms in other countries — with a reply time of a few days, which pedagogically speaking may not have been the worst thing.