Nothing prepares you for people management. You can take courses or read books, but nothing can prepare you for the real experience. That's because you're dealing with people and people are unpredictable.
I once managed a team of people who wrote about computer technology. I had four co-managers who led similar groups but had different areas of concentration. One area in particular included the developer newsletters, which a colleague of mine was in charge of. One day this colleague knocked on my door, looking quite shaken up.
He'd gone in to talk to one of his writers. He tapped on the guy's office door, heard, "Come in," then opened the door. And that's when he saw the writer busy typing away at his desk WEARING NOTHING BUT HIS UNDERWEAR.
For those of you who missed that the first time: WEARING NOTHING BUT HIS UNDERWEAR. You know, I'm not sure what Miss Manners would recommend in such a situation but my friend was, understandably, speechless. What, exactly, is the right thing to do in a situation like that? (Besides a spit-take, that is). Do you put on the greatest poker face ever and go ahead and ask the question you came to ask? My friend could do nothing but stand there until the developer broke the silence with, "Well, it's hot in here."
OK, let's say it was hot in there. Let's say his office was located on the surface of the sun. Would that really give a normal person the idea that it was OK to work in his underwear? I think not. And if you think you could have handled the whole thing smoothly as a manager, well then, my hat is off to you. (But only my hat!)
My point is, books and classes can't possibly predict all the behaviors and situations you will encounter when you lead a group of people. And what's really sad is that I have more stories like this.