My school did that and it helped firing the worse teachers I got :

A simple poll on every course taught during the three year.

[Gonna be surely a long rant since some testimony below]
The previous prom before us got a teacher that went nuts, like the first and only lesson classes was like "Okay so if you don't understand my lessons, you get out. I don't want any question." I'm not kidding.
So since he wanted to teach researching stuff, they had only 4 hours of lessons, and the other classes were to research.
At the exam, he went nuts again and were saying people did shit, saying that they are shit, etc.
Worse is, if you happen to have to do a catch up examen with him, you had to implement in 4 hours a program that took at least 20 hours of research.

But at the end of the year, students got asked with a poll how each classes of the year went. All the prom gave the feedback that was deserved.

The next year, wiht my prom, the teacher was extremely kind with us, but we all knew that was because his job was compromised. (And if I'm not wrong, he doesn't do that course anymore for engineers, fortunatly.)