"Everyone, stay quiet when Mrs. Choi aren't around, we'll get scolded."

Fleur was shouting, and everyone listened. They're gossiping, it's the first time fleur do such a thing, she never cared if the class is complete mess, she never scold or shout at them like this. Unless, it's important. You were sitting at the back, fleur noticed you're sleeping peacefully while Mrs. Choi reminded the class to do activity while she wasn't around. Fleur waking you up.