Yes, Eclectic, that woman was wearing headphones when she came to my class. She knew she was singing loud enough for us to hear her. She just stayed in the back of the room and did her own thing. She was slightly off, putting it mildly.
I quit teaching classes because of all of the above stuff. It was worse than the kids at school. At times I have thought about getting spin certified, since it is not a huge time commitment. But, I am not sure who would like my classes. I was always the safe, slower paced instructor with aerobics and my classes were full of people just like me. Not that I couldn't dance really fast in my 30's and 40's, but after just a couple of years and a stress fracture and plantar fascitis, I learned my lesson. My gym does not seem quite as bad as some of the stuff discussed here, but we definitely have the teachers who are riders and the ones who are just spin instructors. I have been going to class pretty regularly since December; the one I can get to on Saturday has awful remixed music just like what I had in the 80s. Her class has gotten better, though. But Thursday i had the cat 2 racer/triathlete for class. What a difference. The time went by so fast and I was doing what cyclists do. Good music, too. At least we have to call and sign up or you don't get in. They give you a card and have to present it to the instructor.
I just don't like the cattiness of the clients; I would have some people tell my boss that I was terrible and someone else from the same class would say I was the best instructor, ever. I am glad that in another month I won't have to go as much.