We have a dedicated account on KGS that we have access to for teaching Association members.
If you are the teacher:
You can transfer control, by "set players" to allow one or two students to play part of the game for a while, to illustrate a point. Then "take control" back again. This works well for getting them involved, especially for a player whose game it is not.
The 'mark' tools are also invaluable in engaging the students. e.g. mark potential moves A,B,C,D and ask for votes, or to highlight a position, say a weak group or connection. Use of function keys speeds it up. When finished, you have to use the Move tool (F1) to continue the game.
It is recommended that the lecturer has a single pre-prepared SGF file. If you have more than one file, then you will need to exit, load another game into the room and wait for people to connect to it. We have not yet found a good way of merging SGF files. If you have more than one game, you will need to have the second game starting as a branch from move 1.
For one-to-one or one-to-two, using Skype can work better, as everyone has voice, but this can get disruptive with larger numbers, especially as the time lag increases as does voice interference.
We pay for this account, so it is NOT to be used for Rated Games.
You can set the game to "Private" by using File/Upload (P) SGF file to...It’s not clear how the owner then invites only selected people to join the game. [Alison Bexfield may know].
Andrew Simons has used his own teaching account extensively and I expect would be willing to provide help if needed
Note that the account only has teaching privileges (voice etc.) when the teacher loads the game. [This is what I have deduced by experiment; if anyone can clarify the precise restriction, I would like to hear it]. So if playing a 1-1 teaching game, the teacher should load a blank game of the correct board size, place the handicap stones with White passes, then transfer control of Black to the student.
Sept 2013, Updated Jan 2015