I am a parent of a teenage son who is 15 so I am wondering if he can use a VPN to prevent me from monitoring whether he is connected or not (I use this to see whether he uses the internet while I am asleep). Thanks in advance.
A VPN prevents you from inspecting traffic. It does not hide whether or not a connection exists.
Without wanting to get deep into the technical weeds, an Internet connection works on several layers. There’s a physical layer and a transport layer (even with WiFi, this is still a ‘physical layer’) that has to be in place for a connection to be valid and you can always see these on your network.
Connected no you will still see a connection. But what his traffic is you will have no idea besides how much bandwidth
I think all modern operating systems have that now, mobile and desktop. not a bad shout. I know you can work around them if you’re dedicated but they do keep honest people honest at the very least.