Is there a way to fully restrict my child’s texting to approved contacts only?

I’m trying to manage my child’s communication safety and apple makes this so difficult. For example. Trying to even control my child’s contacts I go to my account and I got it to say that I can manage my child’s contacts. I’m doing this so strangers can’t text him. Well, it seems that even if I control it, random strangers are still allowed to text him. All he has to do is add the stranger to his contacts.

isn’t there an easier way to prevent this so that the parent has full control to allow who he can or can’t text? I’ve tried everything and nothing works. Even if I select a setting that says specific contacts. That doesn’t appear when the child is not in down time. This needs to be really worked on Apple. Come on.

[Re-Titled by Moderator]