Sorry but my problem at classes is those individuals who know the teacher very well or kow-tow (sorry about spelling) to a teacher and keep them to themselves.
I agree some are a pain. I was very new to quilting 6months and a lady came and changed my foot fiddled with the machine and went off saying that's better. Luckily the lady by my side was an instructor in her own right and came to me and said do you need help. My reply what did she do? Second lady put it all back.
Although these people think they are being helpful or just showing knowledge they can cause problems as we attend a class to follow the instructors techniques in order to learn.
I have a label it says keep off I place on my machine now. Although I love to chat at coffee breaks and lunch.