Restrict contact editing for a child on Mac
A parent or guardian can use Screen Time to prevent a child from modifying their contact list using the Contacts app on Mac.
On your Mac, do one of the following:
If you’re using Family Sharing: Log in to your Mac user account, then make sure you’re signed in with your Apple ID.
If you aren’t using Family Sharing: Log in to the child’s Mac user account.
Choose Apple menu
> System Preferences, then click Screen Time 
.If you’re using Family Sharing, click the pop-up menu in the sidebar, then choose a child.
Click Options in the sidebar, then make sure Screen Time is on.
If Screen Time isn’t on, click Turn On.
Click Communication in the sidebar, then make sure the “Allow contact editing” tickbox is unselected.
If the child opens the Contacts app on their Mac after this option has been set, the screen time passcode is requested.