The original vision for the tor-teachers@ list was to put hand-selected people on the list to let them together grow a community of leaders and trainers we are mentoring and coordinating around the world.
In practice, the deployment didn't go that way, since it started as just yet another public list that randoms from around the world could subscribe to, and it quickly turned into a place that nobody really valued being. (Same story as the tor-onions@ list now that I think of it -- it was originally going to be for building community between the people running high profile onion services, from Facebook to NYT to BBC to etc, but when we deployed the idea we didn't set it up to succeed.)
So: while you are sunsetting this one, consider if there is still a role to play for a closed community of people around the world that we know are good at teaching, and that we know value Tor, and where we want them to meet each other so they can compare notes and not necessarily have the few paid members of the community team always in between.