As a former substitute teacher for Pre-K to 5th grade music classes, I always liked having age-appropriate sing-along songs handy, that students loved singing. Here are some of my favorites for Pre-K classes (for Pre-K it may be best to share just the chorus, as it helps to keep it simple to maintain their interest):
I’m a Little Teapot (The perfect length for pre-schoolers, and they like the gestures that go along with the song)
Twinkle-Twinkle Little Star (I like songs that focus on science topics) Video with Julia & Elmo
You Are My Sunshine (My mother sang the chorus from this song to me and my daughter when we were both young; the chorus is what I share in class)
It’s an Insect Not a Spider Lyrics and sample available. It is sung to the tune of Oh My Darling, Clementine. This is a great way to clarify to young children that there is a clear difference between insects and spiders.
Head, Shoulders, Knees, and Toes (This is great for getting students moving)