Kids shouldn't even be on the Internet.
I think the problem was when the Internet started hitting the big time late 90s/early 2000s and the government seemed determined to expose every kiddy to the Internet via the school systems, then telling parents that they all had to have a computer and the Internet. Schools should have always been set up on some kind of AOL-alike network with restrictions that make Apple's App Store policies look tame, with the real Internet being something you might start work on in high school once you're starting to learn what this thing called "trust" is, and you're likely already aware of the aforementioned computer game character fetishists.
Anyway, hindsight's a wonderful thing (even if some of us had the foresight to see this Daily Mail wailing happening a long while before it happened), and we've just got to deal with the aftermath of the idiots who made it so it's now almost a necessity to have kids on the Internet. Technologically, a whitelist is probably about the only way you're going to stop someone going on sites you don't want them on, and even that doesn't stop them seeing whatever some hacker decides to graffiti a website's home page with.
A friend has a lovely solution though, that I believe one or two people here already use: The computer is in the living room. Only the older kids have devices that can get on the Internet. If you're somehow a younger reader that's stumbled onto this dark corner of the Internet and think that's cruel or draconian, think about how cruel or draconian a world would be where nobody can have access to an unfettered Internet because of all the "think of the children" wailing? You'll grow up. The rest of us won't^Walready have.
(and please don't tell mum that the Reg has been telling you about Sonic pr0n, I like this site when half the editors haven't been arrested)