I have had sub experience in Art, so I'll add SOME of my ideas.
I once subbed for a guy who wrote a note for me in the morning:
"do whatever you like".
It was a good thing I had art ed. experience- and the often-bashed art ed. TRAINING, for otherwise I would not have had a clue! I began to anticipate days with this school by cranking out some virgin lessons cooked up in the pot of the methods class. I usually had a space of 10-15 minutes to get myself together for the day there. One thing I still remember is the fact that they didn't have glue on their art cart - YES, IN ADDITION IT WAS A TRAVELLING ART CLASS!
I had to mooch some from a 4th grade teacher.... Well, the end to all this was that IF I made a fuss about how poorly this guy had done to prepare for a sub, I would have been passed over in the carnivorous sub list for another, at a time when I was desperate for a foothold- really doing PR instead of making money. So, you are put between a rock and a hard place if you sub. You have to please the teacher, but dare not complain about what is lacking.
I respect the difficult job subs have to do, and NO WAY could I find fault with them for minor transgressions like I've read about.
Now a happily swamped full timer,