Yes, most teachers are really glad if pupils come to them and tell, why they don't say much... or other problems.
I would say, it helps in 95%. If the teacher knows about it, it often gets easier to be more frank with him/her.
And sometimes your sitting neighbor also is important.
In my example, I now have a girl next to me who always says: "Do you know the answer? Well, then raise your hand!" It just feels good to have people who believe in you. And there basicly are more people who believe in you than you think. And as soon as you fell that they believe in you, the pain of saing wrong things gets extremely low.
I first had an English teacher, she was my favorite teacher through all the time we had her in class. I sometimes had the feeling she saw me even more than my own parents. Her lessons were brilliant, I learned a lot and her pronunciation was brilliant. But then she became pregnant... and she never came back.

She's working at another school now. She had hated our class. No wonder: 31 stupid and noisy pupils who dislike every teacher who gives homework and writes tests (I'm the 32nd!

)
Our next teacher was a Native American and I found him really cool. He did beatboxing and he had produced a CD with funny songs which some pupils bought. He made everyone laugh. We never learnde with the schoolbook and he didn't get the class in control. Nevertheless, I learned to understand fast speaking people and how American English is like. And I learned many new words. One time he almost cries lucky tears because of me while I got an inner laughflash...
And our teacher after the Native American went away... no, I don't want to start talking about him right now, that's too difficult to imagine...
