I think the best option would be via 3rd party software. If this is a PC/laptop you could try the parental controls filtering software Qustodio (www.qustodio.com). They offer a free version of the software to give it a try.
I don't think it is possible to disable the Wi-Fi at certain times just for an individual device.
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The easiest way is to log in to your router. There is a function that allows you to block the MAC address of your child's device/devices from accessing the internet at the times you choose. Here is a link to the guide