I'll go further and ask "what if their 'voice' is just bad"? Just because I have a 'voice' doesn't mean it's necessarily good. Teaching students to be able to switch voices - some voices/styles are more appropriate for some types of communications than others. Recognizing these types, and being able to switch... that seems like it would be a thing to teach/learn. My early schooling was a long time ago, and I don't think I had the language to categorize all of this at that time, but I do have memories of doing this sort of stuff (mostly grades 6-8 where I had the same writing teacher, but later with various classes through grade 12).