A funny story. Charlie and I had been talking about trying to get the instructors to let us try out a session in A; but since my times had not improved I had pretty much given up on it. At the end of a session in I that ended with a red flag (accident), I pulled off only to see Charlie at the end of pit out. Assuming that meant that Intermediate was going to go back out, I rode down, jumped off my bike and hit the porta potty (dang Red Bull!), jumped back on the bike and followed him and an instructor out (and they were gone pretty quickly no hope of keeping up). Well, it took me about 3 laps to figure out that I wasn't in Intermediate, I was in ADVANCED (much closer passing and I was getting SMOKED). If you don't know, riding in a group you are not signed up for is a huge no-no and cause for getting tossed off the trackday. After I figure out what I've done, I decided I'd finish the session, since I was gonna get tossed anyway - and it was a good learning experience, being the 'passee' instead of the 'passer' - you just need to keep a consistent line, always leave room on both sides of you and don't do anything unexpected and the A riders will pass you with ease.
I get back in the pits, told Charlie I figured out what I'd done (and they'd given him an A sticker to ride with), and go find the coach expecting to beg for mercy. Fortunately enough, he vouched for me and I escaped a tongue-lashing and getting tossed out. Not to mention 40 minutes worth of riding in one shot was pretty tiring!