At what age can I no longer manage child's Screen Time from my iPhone?

I have a 10 year old and a 13 year old in my Family, and my iPhone gives me the ability to manage Screen Time on their devices. I don't think I did anything special to enable this; my assumption is that iOS just provides this ability because they are children. I also have my adult spouse in my Family, and (of course) I don't have the ability to manage their Screen Time. Question is, at what age will Apple decide that my 13 year old is an adult and stop allowing me to manage their Screen Time from my iPhone? Is there any way to continue to manage their Screen Time after that point in time?