Out of curiosity, my daughter and I conducted an experiment last night.
We went to one of many live CD lists on the net.
http://www.frozentech.com/content/livecd.php
We picked the first live Linux version on the list that neither of us were familiar with --Puppy Linux
Here's the timeline:
Time to download ISO: 12 Minutes
Time to burn ISO: 3 Minutes
Time to boot Live CD on a Laptop: 2 Minutes
Time to get familiar with this particular flavor (distribution) of Linux: 5 minutes
Time to setup network connection: 2 Minutes (Puppy had a wizard for this -- Actually worked well)
Time to find and open web browser: 30 seconds (Puppy comes bundled with Sea Monkey)
In less than thirty minutes we were on the internet with a non-Windows OS. This means that every single client based parental control mentioned on this thread would have been defeated. (This particular flavor of Linux does not even mount the hard drive unless you tell it too.)
Web Watcher, Netnanny, CyberPatrol, Safe Eyes, etc. --All useless and money down the drain.
This even includes the KidSafe Security key whose advertisers claim that, "They've even got processes to keep your computer from booting to a live-cd or other boot device." (That claim is rubbish. With the key removed, there is no way to prevent a cold boot from a live CD short of flashing a new BIOS on the target system and who would want to do that? The Windows install disk itself is a live CD.)
Anyone who doubts that a child from about 13 up is incapable of this should think again. It's not really an issue of "Know how" so much as it is an issue of simply "Knowing." The whole process is no harder than burning a music CD and only a few extra steps are required to make a bootable flash drive instead. If the child has any real interest in computers at all, they'll learn this from their peers. I know this because my daughter told me that her friends were circumventing the Websense security software at her high school with a Knoppix live CD when they were freshmen.
In the end, I don't think there's a substitute for directly supervising the child's internet access in the early years and incrementally relinquishing that control only as the child earns your trust.