One of the first things I start my day with, after the roll, is to tell students who I am, why their teacher is gone, and the plan for the day. I have a mantra I share, "Go With the Flow". I have them repeat it, depending on the feel of the class, we might even sing song it. But the point is, that I am not Mrs/Mr ClassroomTeacher and things will be slightly different than usual. I let them know that we will still follow the teacher's plan but things might seem a bit different and its OKAY!
Some kids just get so anxious when things are different. You start to hear, "Mrs. CT does this." "Mr. CT does it like that." and once that starts, it seems to come up for the rest of the day, over and over.
We can't do things EXACTLY like their teacher, because chances are, we have never been in the room before, never seen them in action.
We know that the anxiety is probably cause by kids being in Piaget's Concrete Stage. We also know that no matter what they say, subconsciously kids thrive on rules and restrictions and continuity. Problem is, it is super hard to provide that in a totally new environment.
If kids hear, right off the bat, that you are going to do your best, but things will be a little different, they know that an inconsistent day is coming, it strangely calms them down.
I will remind them a few times during the day, by saying something like, "Math might seem a little different today, but let's remember to________(Making a wave motion with my arm.)" And usually they can repeat, "Go With The Flow."
When I return to a classroom, they will usually remember that before they remember my name!
I recently returned to a Kindergarten classroom I haven't been in for months and just said, "Hello Ladies and Jellyfish, what are we going to do today?" They made the arm wave motion and started singing, "Go With The Flow! Go With The Flow! Go With The Flow!" The new boy in class cried though because he didn't know the game.