I would add…and the parents legal liabilities for the acts of the child. You as the parent, owner of the network can be held legally liable for various things your child does. You may end up paying the penalties they’re assessed. (illegal downloads of movies and music, illegal sharing of passwords to various sites with friends, copyright violations, selling or trading various things via the web, exchange/access of information available in some portions of the darknet, identity theft, child pornography should one of their friends start sending them illicit material they generate themselves etc.) Also if your child gets involved in theft, drug use or sale, vandalism, and utilizes the web/phone for exchanging information with folks engaging in the activity with them.
When I got my driver’s license my Dad pointed out that if I screwed up in the car and hurt someone or did enough damage-- he could lose his house. It was the only asset he had. If he couldn’t trust me to keep that in mind when driving-- I wasn’t going to be driving.
I agree with those who say you explain to your kid why you’re going to monitor, what the natural consequences as well as legal consequences of misbehavior or misuse can be, not just to themselves but others as well. If you can’t trust them, they don’t get access.
Now, even if you trust your child, and even if they’re not doing anything elicit, you do need to be monitoring their web pages for two reasons. It does give you some insight via their images and posts what they’re up to and mindset, as well as their friends. It may prompt a conversation about why a specific image spoke to them. You may catch something suspicious with your advanced years and additional experience that they miss.
As for bathroom privacy. I don’t believe it gets violated unless you have compelling evidence that something harmful to their safety is going on- drug/alcohol use; cutting themselves etc.
Your kids will always find a way to sneak something past you. Access internet at a friends house or school etc. I think you have to build trust from when they are little and explain that the more they demonstrate their compliance with the rules, their willingness to abide by them, the more you can and will trust them in the future. You need to show me now that I can trust you when you’re somewhere else because you’re going to want to drive places when you’re in high school, go places with your friends. Show me I can trust you now, and I’ll know I can trust you then. Break my trust now, and I’ll have a hard time trusting you in the future. Always harder to rebuild trust after it has been violated. Which goes two ways. You break their trust on something key, incredibly difficult to rebuild.