I use Family Wifi to group my son's devices into 1 group and pause his devices as and when required. However, he can still access the internet by switching off the wifi connectivity on his laptop and switching it on again. In the end, i can see many duplicates of the same devices on my Google Home that is not in the family wifi group. Pls help. Thks.
Do all these devices have the same IP and MAC address?
You could try setting up a static IP for that device to see if that helps somehow.
It sounds like your son's laptop may have "random hardware addresses" enabled. Take a look at this support page from Microsoft: https://support.microsoft.com/en-us/windows/how-to-use-random-hardware-addresses-in-windows-ac58de34...
Those explain how to enable it, but you should be able to follow them to check whether it's enabled and then disable it. However, if your son is intentionally using this feature to get around the network-level pausing, you may find that disabling this feature won't stop him from enabling it again. When I was getting my son through this period, I used operating system level tools from Apple (e.g., "Screen Time") and Microsoft ("Microsoft Family") to manage screen time instead of trying to use the network-level tools that, frankly, are becoming less effective as random MAC address and other features become more prevalent. So, you might consider looking into those features as well.