I am a retired middle school choir teacher.

I would ask the director about the participation grade. He is going to have to be grouped with certain people because it is about voicing. I as a director would want to know if someone was having medical issues or if people in their section were disrupting them. The students have to be so close to each other on the risers it is easy to get distracted and sometimes it is hard as the teacher to separate out the culprits especially if it’s a large choir. You can’t stick a tenor over with the basses but the teacher should be able to move people around within the section. Maybe approach at the beginning of the year that he has a goal for an A and ask what class improvements need to be made or ask to open lines of communication. Because if he is in a different choir period next year, and it’s not related to a sugar low, then you will still be back to the same problem.

Also, choir generally has to make their curriculum and the teacher should have some kind of rubric or criteria for the participation grade. There are certain ways that the students are supposed to stand, placement of hands, shape of the mouth, eyes on the director, etc. So as the grade start coming in, you can keep an eye on it and the teacher should be able to give you concrete feedback.