Parental control software - help?!

[HmmmIwonder]

Can any of you clever people explain to me how parental control software works, and any advice on how to choose a good one from the hundreds that come up when you google it?
your help would be much appreciated, thanks!

I have big brother. Which monitors everything done on the PC. You log into the user interface and can see which websites have been visited. It records all of the key strokes and screen snapshots.

You can get some which just allow you to block the use of certain sites, but I found them ineffective. As you are blocking the sites of a user on the pc. All the DCs need to do is create a new user and they can do what they want.