Yep that's what happens to me, it's the weirdest thing. Today I had a slightly different version. in the dream, I was actually thinking about those very dreams that I get. Then while thinking about the dream I realize that I really was missing a bunch of classes. Was trying to think of what the classes were, I knew it was math, and a bunch of others, and then it occurred to me that I kept going home after lunch, for some reason that just became my routine. Show up for the morning classes, eat lunch, then go home. So I was missing all the afternoon classes. I was panicking for a moment, then woke up, still panicking, then a sigh of relief when i realized I'm not actually in school anymore.
It probably has to do with the fact that schooling is a huge chunk of one's life, so even when it's over, your mind is kinda still in that same mindset. It probably never goes away completely. Having to do good on a test, etc.