Repeat after me: Children are not small adults.
It's true and it sounds obvious but it's not. Every day I read posts from teachers lamenting about 7-year-olds that can't just "sit still and read the notes".
Is that what music is? Sitting still and reading notes? I'm *cough* a good bit older than 7 and I have trouble just sitting still for too long. When I play in the ballet studio I'm so grateful that it's socially acceptable for me to just stand up between songs or stretch my shoulders.
Without further ado here are my top 3 tips for teaching young singers. (and I have a hunch they might go over pretty well with singers of all ages)
ASK young singers what they want to sing. And then LET THEM SING IT! There doesn't need to be a standard repertoire list. If the child loves the song they'll sing it better than something you force on them because it's "good for them" (what does that even mean anyway? Never mind- that's another post)
ENCOURAGE young singers to pay attention to how they experience sound. When something sounds good ask them to take note of where the sound came from in their bodies. Ask them to tell you how it felt INSTEAD of explaining how you perceive sound in your body. I promise- they will remember their own explanation better than yours.
PLAY with the voice. Spend time at every lesson discovering all the things your voice can do. Make high siren sounds and low grumbles. Roar like a lion and hoot like an owl. Try on different accents for size. You don't have to be particularly good at any of these things. Just explore the voice.
Remember that there's a good chance your student came to you already loving singing. Your priority is to nurture that love and watch it grow!