Facial expression is actually an essential part of choral singing. Your teacher probably spoke to your class about it, and it requires deliberate thought in order to portray the emotions in the music. It’s a lot like needing facial and vocal expression in a drama class.Unless your instructor never mentioned this, this is on you.

this is actually a real critique. Facial expressions aren't just for making you look good as you sing. the way you make your mouth move is essential for changing the sound and enounciating the words you're supposed to be singing.

Obviously you're not a "wonderful" singer if you got a B. More like a slightly above average singer.

I’ve taken many years of choir and individual vocal instruction and facial expression is incredibly important. It helps with placement, projection, and over all tone. If your face isn’t lifted you’ll sing flat. Every instructor I’ve ever had, and every level, has spoken about facial expression. It’s a very conscious effort to do so, it probably looked like you either didn’t care enough to try or that you were not paying attention during instruction.

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OP here. Yeah, I understand that facial expression is part of being a performer. My problem was that she never said anything to me before (no warning). Also, there’s a bunch of my peers don’t sing at all or they’re just playing/laughing, yet they have A’s

If you can sing at a sufficient level for a high grade maintaining said face... I'd like to know quite how you'd manage that.