Blocked Sites from Gateway Interface,... not blocked.

Bonjour y'all,

have recently (ca 1 month) switch to XFinity and kids are remote-learners. I'd like to prevent them from surfing youTube during their school time and have tried to set it up from the gateway interface (10.0.0.1), but to no avail.

Does anyone have a trick to make that happen?

Merci!

PF ROUX