I added YouTube.com under the restricted sites (not specifically as an adult site, just restricted) and it did stop my kids from going there directly, but they figured out that they can Shazam a song, use its “show song on Youtube” feature to get a fully functioning YouTube page and start working from there.

They can’t even read yet.

I am at the same time very proud at the l33t hacking skills and upset at their disregard for rules. But mostly proud.

I will check if “adult” blocking works better.