I think that you are looking for a technological solution to a non technological problem, even if there was no encryption at all there is no way to 100% inspect

I think that you are looking for a technological solution to a non technological problem, even if there was no encryption at all there is no way to 100% inspect all of your kids communications. The same way there is no way to follow them and watch them 100% of the time in the real world. The only thing you can do is educate your kid about these issues and trust them.