Texts sent/recieved from child account visible to Parents

Hi All,

Just got my youngest a phone and rather than have him continue to use my icloud account to text his friends I've set him up with a child account so that he can have his own contacts, music library, etc. Our deal though was I have access to his messages, I know I can do it if he continues to use my iCloud account, but isn't there a way to add the chile account to my phone?

Feels like that should be a thing....