Hello @ClearwaterCJ
That sounds frustrating, and having been through those years as a parent as well, I know just how frustrating it can be. What he's doing here is changing the MAC address of the computer, which makes it look like a new and different machine to the network, which then happily assigns a new IP address to it. This does bypass the scheduled pausing. There are a few things that can be done to improve the situation. First, make sure you have "New device" notifications enabled for both the main and guest network, and I would also enable "Password mismatches" in there as well (In the Google Home app, tap the "Wi-Fi" bubble at the top of the main screen, then tap the gear icon at the top of the next screen, and then tap "Notification settings"). What this will do is generate a notification on your phone any time a "new" device connects (and remember that he's changing the MAC address to make his computer look like it's "new" to your network). However, since you may be asleep when this happens, it may not be sufficient.
The next thing you can do is change the WiFi password on your primary network (yes, this will require reconfiguring everything you want on that network, so consider this optional), and create a "guest" network. Then, configure his computer to connect only to the guest network. At bed time, disable the guest network. As long as he doesn't know the password to the primary network, his machine won't be able to connect via WiFi. This only works if he hasn't been added to the Google Home as a "member" of the home (because anyone with that access can see and change any of the WiFi settings).
Those are the things that can be done at the network level, and as you can see, they are far from perfect (but they are limitations of what is possible with consumer networking solutions). The next level up from there may be more effective and convenient: use the parental controls built in to the computer's operating system itself. Microsoft "Family" has some pretty nice tools for managing screen time on Windows and Xbox, for example. For this to work, the computer has to be locked down a bit so he can't create a new local account, etc., but once set up, it can help provide more constraints.
All of that said, technology may just not be the best solution to this particular issue. I did use the operating system parental controls features, but the thing that helped the most was just not having any electronic devices in bedrooms after bed time. I wish you the very best of luck in getting through these more challenging years.
