What exactly do you think I'm doing here?

When substitute teaching, I occasionally get time to chat with the children, and often they will ask me questions about where I went to high school, where I went to college, what I studied, etc.  Usually these questions are fairly mundane and I'm actually a bit shocked that the children haven't thought of something more creative, but there is one question that I've gotten twice now.

"What do you do?"

Meaning, what do I do for a job.  My answer?

"I substitute teach."

Kids!  What do you think I'm doing here all day?  Just showing up at your school to hang out with teenagers?  No thank you.  I get paid for this.  I always pause for the briefest of moments before answering this question because I truthfully can't believe they don't know what my job is.  They are literally watching me do my job and yet still wonder how I make a living.  And yes, I realize that they assume this isn't a permanent job for me, and hopefully it isn't, but it is what I currently do.  Oh children.  Please never change.