In 2nd grade with either of my kids, we (DP or I) would have requested an appointment with the teacher and then been there to facilitate the conversation for a major issue. We went in several times with DD from 2nd-3rd grade to be there while she talked to the teacher. That way she had support and we could make sure she said everything she meant to say. This year DS is in 2nd grade and he reports small issues with no problem, but we will go in a few minutes before or after school so he can talk to his teacher without other kids being present. For a minor issue we would expect the child to bring it up themself.
When DD was nine she felt a homework assignment due date was unfair. She was able to bring it up in class and make a good enough arguement in front of the class that the teacher changed it. At 7 we had an appointment with the teacher where she told her she considered parents having to "okay" homework assignments was demeaning.

The teacher had never heard that one before and happily had us NOT sign stuff that came home as long as DD kept up her side of the bargain.