Ok, so say a filter system existed that blocked all pr0n from the googles of the world.

Get creative with some addresses - I remember being a student (pre-google days) and playing a game where you'd put a random non sexual word into the browser's address bar followed by a .com and seeing how many sites came back were pr0n. Hint - a lot!

Ok so this trick is clamped down on and sophisticated filters now block all content if it's pr0n, so the internet is no good.

Guess what, pr0n existed before the internet! All manner of filthy videos and mags did the rounds when I was in school (pre-internet becoming the norm).

The usual source of the "goods"?

1. one of the lads would go on a trip to Europe (with scouts etc.) and visit pretty much any news-stand in mainland Europe

2. someone would liberate some from their parents stash

So filter/block/remove it all from the internet and the kids will go back to the old fashioned way of getting at the stuff.

Incidentally by the age of 13 I'd seen some pretty hardcore stuff. Hasn't done me any harm either!