Not promoting any brand or maker, rather the novice student is best surrounded by experts like teachers.
You are right some teachers are promoting "their" brands, but this is often the accordion brand/maker that is to be blamed. Because many times Italian or other makers only make 1 person a representative for his brand in a country. The maker offers a % per accordion sold by the teacher to the student.
This off course leads to this 1 person ( a dealer or dealer-teacher) trying to catch as many teachers and his/her students, to sell as much instruments as possible.
This % reduction is a benefit for the teacher and for the student, it's common practice. But in my experience most of the times the Italian top brands are used by the teachers (Bugari, Pigini, Borsini, Mengascini, Brandoni, ... etc) or the German brands. So I don't think the teachers will sell bad low quality instruments.
They sometimes do have a tendency for pushing young kids to buy an accordion that is too big and too heavy for a child, because they want to save the student from upgrading to a larger instruments, and so spending money on 2 accordions. They do this when they think the kid/student has got talent and ambition for conservatory studies.
The real challenge is to make distinction between good teachers and the teacher-dealers with focus on selling only.
This is the same for piano , cello and violin teachers.
Good teachers only recommend good instruments, because they know cheap low quality (Chinese etc.) accordions very often lead to poor playing habits. Bellows too stiff, action too slow, reeds poorly tuned (or even only machine tuned, without manual fine tuning...). A bad instrument will always lead to poor playing, this is the same with cheap "classical" guitars, poor strings and multi layered fake-wooden top. And teachers know you can never correct bad playing habits with a bad music instrument, so a good teacher will always try to avoid his student to play on a poor instrument.
Teachers can do some preselection and propose a selection of good brands to the students. The teacher can invite a multitude of brands/makers in his accordion classroom, or he/she could visit music fairs with students and try the accordions. But it's true the %-system used by the Italian makers has been around for a long time, because the 3 parties can benefit (the maker sells to the dealer, the teacher gets his % from the dealer, and the student gets his % from the dealer when in presence of the teacher). Nobody is obliged to buy a certain brand.
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