Is there any specific word or phrases to describe teacher of teachers?
If not, how do I express this idea?
More precisely,someone who train people to be teachers on their fields.
Thank you very much!
If you are referring to the actual person who trains other people to be teachers, the answer is a teacher! A teacher, mentor, instructor is one who prepares a student to take on greater tasks later in life. That student can later decide to become a teacher himself.
If the student is being specifically prepared to take on a teacher role, the one teaching him/her is still a teacher, and subject being thought is well...teaching!
However, if you need to express the idea that those whom he teaches became teachers themselves, you can say:
His students grew up to be teachers themselves.
His students later became teachers.
If you are referring to an institution, as @choster suggested, you can use teacher's colleges which are traditionally known as institutions that prepare people for being teachers.
From ‘The Profession of Teacher Educator in Europe’ (European Commission, 2010) (pdf ~7.71 kB)
Who are Teacher Educators?
16 The PLA adopted as a working definition of Teacher Educator: “All those who actively facilitate the (formal) learning of student teachers and teachers”. This includes those involved in the continuing professional development of teachers as well as those involved in Initial Teacher Education. (emphasis added)
Teacher Educators: What Do We Know? ERIC Digest 15, (Ducharme, Edward R., 1986)
For some, the term teacher educator includes all who instruct prospective and practicing teachers from the instructor of freshman composition to the instructor of learning theory. For others, the term includes only instructors of professional teacher education courses such as methods of teaching reading.
However, there are several other terms applied in various countries and in a variety of similar or closely related descriptions.
I guess the word you are looking for is "GURU"
the Dictionary meaning of guru (noun) is: authority, expert, leader, master, pundit, arbiter, Svengali, torchbearer, fundi (S. African) teacher, mentor, sage, tutor, mahatma, guiding light, swami, maharishi.
Now how can one use this word as teachers teacher or teacher of teachers. To answer that I have used reference of Ancient Hindu civilization from where this word has originated.
To make it simple, assume their is an individual called GS. GS is an all subject expert and he teaches his subject knowledge to two students K and B. After some years B teaches his subject knowledge to students B1 and B2. Please note that what B has mastered from GS is a very unique skill set and their is no one who can beat him(B) in that particular subject matter except GS off course, because he is the teacher here.
Now since B is also teacher of B1 and B2 what should we call GS? Because at any day GS is omniscient among all. The word used in Hinduism is "GURU".
IF you want to dig deep in Hinduism or by chance want to know more about GURU ask/google yourself the names of following individuals. GS here is GURU SANDAPANI. K & B are KRISHNA and BALRAM. B1 & B2 are BHIMA and DURYODHAN respectively.
Hope this helps you address the venerable person with all due respect you seek.