How to change adult xbox account to child account?

I can't remember 100% but I am sure whoever set up the child account can change it. Like if you made an adult account on the xbox before making the child account that adult account can change wether the child account is a child account or and adult one.
I will just test this out myself now and post how it went

How to change child account to an adult account

As said there is no way to change your child's account to an adult account until the age of birth you have put has reached the age of an Adult for your specific region. There are some troubleshooting tips that if your account is past the birthday and still
a child's account there is a way to promote to an adult account.

https://answers.microsoft.com/en-us/windows/forum/games_windows_10/how-to-change-child-account-to-ad...

You can change a child account to an adult account, but you can't change an adult account to a child account. In order to manage them, you would have to create new child accounts for them.

Hey Xwarrior,

Did this account graduate naturally from a child account to an adult account or was there a birthday change attempt? You can change the birthdate to the Microsoft account but it will not change the birthdate that was entered originally to the Xbox profile.

In other words, a child account will remain a child account until it graduates naturally to an adult account. No way around it.