It sure sounds like a "rough justice" way to start the year, and I'm sorry your son was so hurt by it, but I have mixed thoughts on the topic generally.
I agree that starting on the first day is a good thing. The teacher needs to establish the standards and then stick to them. Hopefully your child now understands that kicking is not an acceptable way to express frustration, and will be able to find a suitable replacement (I know, far easier said than done, but that may be the direction you need to emphasize).
DS's first grade teacher kept changing the rules on him, apparently without explaining anything, and it seemed like every time he started to succeed she'd up the ante. On the other hand, I can see that as the school year progresses the teacher should be able to heighten the expectations accordingly, but not without explanation.
