Hi Sue and Emmy,
Sue, I did the same thing that you are doing (I taught third grade for seven years before art), and I don't think you will regret the move! Congrats to you both.
I started out teaching the same element or principle of art for all my elementary grade levels. I have learned to think about the prep of the lessons. I tried to keep a few of my classes with easy prep and a few with more time consuming prep. If at all possible, keeping grade levels back to back is very helpful in planning.
When I started teaching art, it was the first structured art class my students had and the elements were very important. Now, I am finding that they are getting very strong in the elements and need something different. So this year I am going to be teaching a movement in art per month and creating a timeline with all my students. I now plan to have a rotation every few years. Elements of art, Art Movements, Artist a Month, etc. This was an AH HA! idea I got from the national conference. I haven't tried it yet, but I am very excited to try it out this year, especially with the King Tut exhibit in San Francisco that I hope to take a few classes to this fall.
Ultimately, classroom management is the most important part of teaching in my opinion. Harry Wong's book is great. Procedures are key! I give each table a name (line, form, shape, etc. - this year it will be Cave Artists, Gothic Artists, Impressionists, etc.) I also pick one student at the end of class to be my Master Artist the next week. This student has show exemplary attitude and effort. I give the student a 'Master Artist Bookmark' to remind them and to show their parents. The following week that student is my helper for the day (passes out sketchbooks, materials, demonstrates techniques).
I realize this post is probably scattered. I am certainly not back into school mode yet, but I hope it helps a little.
Art Teacher/ Beginning Teacher Mentor
Whitmore Charter School of the Arts and Technology