When the child finishes the song make him/her listens to their own voice. Instruct the child to learn how to examine their progress critically and how to work on over their mistakes to improvise.
Save different recorded songs sung during the practice to make to notice the differences and track the progress.
Save the recordings of the same song on a longer period of time, it helps in tracking the progress. When the child improves, listening to the old recordings will let the child hear just how far he/she has come.
Try again. Each time you record the child’s singing a particular song, help him/her try to be more careful while singing. Be more passionate, or heartfelt, or whatever emotion the song is conveying. Make the child understand how important it is to try and feel the song.
It’s not advisable to start with trying to imitate the voice of a certain artist if that artist belongs to the opposite sex. If you insist on doing that, don’t actually try to copy their voice; sing at your normal pitch.
Everyone is good at something, and if you have a heart for singing or whatever it is then don’t let anyone stop you from trying or doing it. If someone or anyone puts you down and tells you, you can’t sing or you can’t do it, ignore them. Do not compare yourself or your kids to other singers as every voice is unique. If it’s something you really love to do, prove to them that you can do it. Don’t be worried if you think your child’s voice sounds bad. Their voice sometimes may sound weird to you. Ask a family member or friend to listen to them sing so they can tell you how they sound. Talk to your family, tell them how important it is for you and your kids, and assure them that, even if that means having to stand some horrible noises for a while, you will improve and then it will be a pleasure to listen to you.