Parental controls don't help
My parents recently got new computers, and my mother’s old (but still pretty modern) Mac Mini has more or less become my daughter’s. It’s what she’s been using to play Minecraft, as I mentioned recently. OS X has a “Parental Controls” system, and I figured it would be useful. I’d tell it to use its default anti-porn web blacklist, to have a list of (say) ten allowed applications, and to limit her instant messaging to a few approved people. It was a big mess.