Google WiFi has found an answer to this concern. There is a provision in the settings to group the devices you have connected to Wi-Fi and “pause” the devices your children are using. You can set this up for when your children are out of your supervision, or just after you bid them goodnigh
Look at the screen shots.. Looks like a super old device. The images all say **bleep** and one says if it's an emergency, they will flee and we won't be informed.
