change adult account to child account

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.

Is the account in question a child's or adult's account? If its a child account you may want to change it to an adult account and give it a shot.

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

Hello PhilipBasgal,

Thank you for posting on the Xbox forums. We understand that you are interested in changing a child account to an adult account. Once an account has been established as a child account, it cannot be changed to an adult account until the child turns
18. The best way to manage the child account is to
add it to a family. This requires an adult account to add the child account to the family. Once the child account has been added to the adult account's family, the child account will be able to access online features. Be sure to let us know the results!

Only a parental (adult account) can change the privacy settings for a child account. Your parents should open an adult account and add your child account to it.