child changing time screen time!

Our teenager can simply change the time on his phone to bypass screen time restrictions during certain times. I have read about how to prevent time zone changes, which I did, but the time by itself can still be changed. I assume there is no further option for preventing this but apple needs to continue to improve the screen time features. OR not allow access to the settings app, which currently you can't restrict access to. Anyone deal with this also with any fixes?