My congregation is small, and so I am required to pursue alternative sources of income from time to time. Right now, that means substitute teaching. I have 'subbed' in high school, elementary, grades 5, 4, & 3, and just recently in Kindergarten!
The toughest by far is the Kindergarten! They will kill you if you are not prepared. Kindergarten Cop (the movie) underplayed the issue - although I felt just like Schwartzenagger looked after his first day. WOW.
They have boundless energy. They have a million questions. They have not quite learned to sit and listen. Some of them are incapable of following directions unless you are standing right over them. It is not that they are not bright - they ARE. The problem is that they haven't learned school yet.
I had one kid I helped find a number on a chart of 100 -- ten rows of tens - 1-10, 11-20, 21-30, and, well you get the idea. This young lady couldn't find 36, so I showed her how to find the six in the top row and trace down the column with her finger to the 36. She did it easily, and was delighted to accomplish the task. I returned to the front of the room and gave them a new number to find, 44. As I led the class through the same series of instructions, find the four in the top row, and trace down to the 44, the young lady couldn't quite get it done. The entire day went like that, with different children having different challenges.
I don't know what they pay the regular Kindergarten teacher, but it isn't nearly what she is worth!