If you can identify a friend or family member from their voice on the phone, or recognise a tune in a version you've not heard before, then chances are you're not "tone-deaf" - most likely what's lacking is the control of the voice to match it to what you hear.

Like any skill, it takes time to develop, and if children don't get the support they need (and some will need more than others), they're likely to get discourage and not develop it fully. Which is a shame.