Glitter Germs for @Sarah Weingartz and @Laura S Put it on three people's hands and then have everyone, shake hands with everyone. Notice how the "germs" spread! A variation is using this idea to demonstrate how your positive or negative attitude can spread.
Weather: Fill the cup with water. Put shaving cream on top for a cloud. Explain that when clouds get really heavy with water, it rains! Then put blue food coloring on top of the cloud, and watch it rain. Kids love experiments!
First, teacher blows some bubbles and, as expected, the kids all pop them. Then, she challenges them to NOT pop the bubbles even if one lands on the tip of their nose. Introduce the concept of self control and launch a discussion about stopping to think before you act. You can refer back to the lesson again and again. "Think about that time when we didn't pop the bubbles..."
I am in LOVE with this blog post about Meet the Teacher night!! So many great tips on how she runs things including the student packets, helping hands for supplies, and treats for students and parents.