In order to create confidence, children must learn the songs well. Constantly ask yourself, "If I were learning this song, what would I need?" It may mean using word sheets or overhead transparencies. It may mean using hand signs, like a reaching gesture for the word reach, and other simple movements that are powerful tools for teaching by rote. Teaching the song will definitely require repetition, particularly if you teach by rote. Repeat the words. Repeat the phrases. Repeat longer phrases. Then, when you sing the song again a week later, ask yourself, "If I had learned this song a week ago, would I remember it now?"
But don't let the rote process become dumbing down. Children must work at remembering what you teach. When teaching older youth, some song leaders say, "I'll give you your part twice and that's all. You have to get it." They will.
We all learn differently. Some of us benefit from hand signs and movement, while others need word sheets. Still others simply need to listen to the melodies. All of us benefit from repetition.