From Alice Mercer: I believe in second chances. I've experienced it too often myself. I get sloppy, and let stuff slide, then I have to rein things back in. In my first few assignments, I took over abandoned classes. While it's better to make a good first impression, I don't think you need to write off a year or semester that has gotten off track. Here are some posts to consider:

From Larry Ferlazzo reflects on turning it around
From Mathew Needleman on appropriate consequences, and starts with the great quote, "They're not bored, you're boring."
and this on Teacher Voice
And the creator of this wiki shows how to bend the rule to fit the child here.

Micheale Sommerville points out why public humiliation should not be part of your discipline mix, even with the youngsters.