Am not a teacher and neither do I have any experience teaching pupils. But from my past experience as a student, I know being a teacher is a tough job.
Being a good teacher isn't just about having the basic knowledge and equipping yourself with studies from research in order to educate pupils, this is one almost any focus person can execute. But the part that makes you an actual teacher, are situations where you have to employ discipline and make certain you're heard as a teacher.
This takes me back to my early school days. They were some teachers which were generally disliked by students. Not because they didn't know what they were doing, but because their style of teaching and methods wasn't quiet effective. Most student would end up bored through out the period.
My point is, a good teacher isn't just about passing knowledge, it's also about understanding your students and devicing the best way possible to teach. So, yes again, being a teacher is really a tough job to take on.