Re lateness - I once had an instructor who started EARLY, much to my annoyance! I would consider myself an organised person who always has her supplies ready etc. and take classes regularly at my LQS.
As a new quilter, I took a class one day knowing I needed some heavyweight Bondaweb. When I booked the class, I was told I could just buy it on the day (it's the only LQS in my area). I arrived in plenty of time to set up and another lady and I went to the counter. There followed a longish delay whilst this lady had all her fabric etc cut. When it got to my turn, she couldn't find the Bondaweb I needed and eventually I had to buy a very light weight (which irritated me). When I returned to the class area, the instructor had already started - five minutes before the scheduled time and aware I was at the counter!
I never went to one of her classes again. A couple of times after that the LQS class didn't have the item needed for class, one time having to copy a pattern that hadn't arrived in time. I now make sure I have everything the minute I have the supply list and order elsewhere if necessary, before going to the class.