I think many teachers (almost all that I know, and all of the good ones) would disagree with you on that. Lesson planning, training/continuing education, scheduling, etc.

> many of them find side jobs

..why?

That is to say, I'm sure most people on here could get a side job if they wanted to. Is there a reason why teachers get side jobs and, say, programmers don't? (Yes, that's a rhetorical question.)