Earlier on this site, the subject of singing was addressed (listed under "Bible Class Schedule - Singing #5") and the idea of making up your own songs was mentioned. I would like to revisit this topic and encourage all to think of a simple child's tune without the original words and write new words to the music. There are many tunes, "Skip To My Lou," "London Bridge Is Falling Down," "Twinkle, Twinkle, Little Star," to which you could customize a song to fit the lesson you plan on teaching. Children would not need to memorize a new tune and new words, only the new words. Half of your work is already done!
Bear in mind, the only true criteria is that the song must be biblical. (1 Cor. 14:15; Eph. 5:19; Col. 3:16; Jas. 5:13) In public school or driving somewhere in the car, it would not matter if the song was biblical, but in Bible school, all songs must have Bible truths.
Try it! For example, the words could help a child remember the days of creation in order or perhaps learn the names of the sons of Jacob or maybe you could choose a verse in the Bible and see if the tune fits with those words. Many years ago when my children were younger, we studied the topic of singing in a Bible class and did this exact same exercise: Insert a Bible verse into a familiar tune. They still remember some of the songs they composed!
I will offer you an example of a song that I wrote in Salinas, California in the 1980's, and I still use this song to begin many Bible classes. Maybe you will find it helpful, too. (Just click on the orange arrow below for the tune!) I'll be adding more songs from time to time.