One of the smaller Guilds in Ankh-Morpork. Their clock is the first to strike noon, probably answering its members' prayers.
The last mentioned head of the guild was Master Greetling (in Guards! Guards!). At this point the guild was so lowly in the pecking order that for a civic function, it ranked alongside the old, despised, four-man Night Watch in importance and prestige, and got seating to match. As the concept of the teacher on the Disc has since evolved to incorporate more functional and capable pedagogues such as Ronald Saveloy, and super-capable classroom colossi such as Susan Sto Helit (a woman capable of effortlessly outnumbering the kids by a factor of one to thirty), and both of these must have needed to be Guild members in order to practice, then what's the betting that the Guild is now headed by a tougher and harder negotiator who has got a far better position at civic meetings?
The irresistible picture created here is one of Vetinari having to face down a resurgent Teachers' Guild led by a teacher with the combat experience of a Ronald Saveloy. It should also be borne in mind here that the Assassins' Guild runs its own school. In keeping with the principles of demarcation and good inter-Guild relationships, must those Assassins who choose a life of teaching at this particular school take up membership of the Teachers' Guild, in order to be able to practice as teachers? After all, we know the Assassins are absolutely correct in respecting the rights of other Guilds, and honour them to the very letter of protocol, as their sense of noblesse oblige dictates. (And having a legitimate major interest in another Guild must surely be useful, too, for both sides? Similarly, are those who teach at the Thieves' Guild school, in the interests of respecting the rights of a fellow Guild, also obliged to be Teachers' Guild members? If nothing else, this cross-membership ought to bring the Teachers more respect.) It is not known if teaching witches such as Perspicacia Tick and Gammer Brevis are Guild members, but as Gammer runs a village school in Lancre, and is known for being reasonable to an extent that brings Granny Weatherwax to a state of boiling fury, it would appear very probable - as well as giving the Guild extra muscle.
Now imagine Vetinari. Negotiating with a Ronald Saveloy, backed up by Miss Alice Band at his left and Susan Sto Helit on his right. It gets less and less easy, this being a working tyrant...
As the general interpretation of the word "teacher" would only cover one who teaches to children of school age, the teaching faculty at Unseen University are likely to have an opt-out clause, or else an alternative arrangement of their own (just as in Great Britain on Roundworld, a distinction is made between school teachers on the one hand and University and college lecturers on the other). See also entries on Teacher and Travelling Teachers.