Four or five times I have walked into a classroom, have started a class and have been told by a student  -- usually a young female -- right off the bat and without provocation, "You know, we hate substitute teachers."  This is part of high school culture.  It has evidently been part of high school culture for many years because when I've told middle-aged friends that I have been substitute teaching, most of the time they comment that when they were in school they used to give their substitute teachers a hard time.  My usual response when confronted this way is to say as casually as possible, "I didn't come here for love.  If I wanted love, I would get a dog."