There is nothing more satisfying as a substitute than working with a class a second (or third) time and seeing the kids' reactions when they see that you're back in their classroom. It's that special look that says, "Oh no, not this bitch again!" If you're every feeling really depressed or insignificant, I recommend immersing yourself in this situation; it will warm your heart.
I spent the morning with a class I had a few weeks ago. Yeesh. I notice that kids at this school tend to be more unruly than at my other schools, although I also wonder if it's behavior confirmation on my part. Anyway, I had this class before, and they would not just quiet down so we could... well, do anything. At the beginning of the day I wrote "RECESS" on the board and told them that every time they took too long to quiet down I would erase part of a letter and they would lose time from their recess. The way I explained it, if they were going to waste my teaching time then I was going to waste their fun time. They didn't get recess that day. Even if I had a change of heart that morning they would not have been able to go outside because they would not stop talking long enough to get lined up. So you can imagine their joy when they walked into school this morning and saw my smiling face in the classroom. But you know what happened today? They were better behaved. It's nice being able to say to a class, "You have had me before. You know I am not kidding. You know what will happen if you break my rules." And it's a good thing that they didn't owe me time today, because it was gorgeous outside and I would have been super upset if I missed my recess.
I would be overselling the effectiveness of clear expectations if I didn't mention this confounding variable: I also used an incentive program with them that I didn't use last time. I am inconsistent with using this program since I like to feel out a class first, but here's the basic premise: if a student is doing a good job, they get a post-it or index card (depending on what is in my Mary Poppins bag at the time). Whenever I catch them doing what they're supposed to, they get a stamp/signature/sticker (again, depending on the vagaries of the bag). If they get a predetermined number of stamps/signatures/stickers by the end of our time together, they get a prize. If they start getting off-task they can lose stamps/signatures/stickers. With classes like these it's a great way to give students constant feedback, and even though I would never do something like this as a regular teacher, I find that as a substitute it can be nice to have a more immediate reward dangling in front of them than, "I'll give you a [insert mascot here] dollar so you can eventually get a pencil from the school store." Is it bribery? Yes. Is it effective? Usually. And since I have this class again in a few days, I'm betting that they'll be as good as they were today because they know the consequences for their behavior, both positive and negative.
One more braggy note before I go: I got two recesses today! I went to kindergarten for the afternoon (a class I taught yesterday) and got to spend a full 30 minutes outside with them. It was nice getting to see two very different ages today: it reminded me what was great about both.Then again, that could just be the sunshine talking.