I just saw this, but then, I'm not here every day.
Is your experience acceptable practice? No. Normal? Unfortunately, in my experience, yes. Here's how my attempts on both ends have gone:
1983: Oh, gee, the community college has a class! Call ahead because road is slick--yes, we're still having it--drive fifteen miles to site, find one person taking names "in case we have the class later".
1984: Say, there's a knitting group at the library! Go, then get yelled at because they all knit in one very specific Enfglish style with one brand of very expensive yarn.
19...99, I think?: Hey, there's a new yarn shop and they have classes! It's a long drive, but it's a LYS and I have to see this. Go and find a couple of shelves of novelty yarn with list price tags pasted halfway over the discount store's lower tag. There were classes listed, but half of them were canceled.
I'm not going to list the places and times I've taught, in case it might hurt someone's feelings, but the bottom of the barrel for me was a largish class in which one student had no idea what she had gotten into even though a detailed description was on the sign-up sheet. When I handed out a line-by-line, no abbreviations, beginner detailed pattern, she immediately started to cry and yell that it was too long and she would never be able to finish. Her tears and screaming (yes, literally) drove off half the class at the first session. I still feel terrible about that and it was years ago.
In the best classes, the students knew what was going to be included in the class, paid attention to the starting time (and so did the shop owner!), listened to the introductory remarks instead of wandering off, and waited for help before tearing anything out. For instance, it's hard to explain to a new knitter that ribbing usually looks like junk for three or four rows, then seems to fall into shape. If they give up and frog instead of asking for help, everything has to stop while they get started again. I finally had to make a "no frogging without asking" rule and gently dismissed anyone who ripped out the work for a third time without asking whether anything was actually wrong.