Firstly, im 14.
I have the Router in my room, full access to wireless and wired connections, a PS3, an Xbox 360, a PC, iPod Touch, And a PSP Slim. The router is never turned off, and im not restricted in anyway. I am in control of the network, not my dad.
I have never had any compelling reason to talk to strangers online (Online gaming does not count, you are there to game, not talk, i mean through PC) I dont do stupid things on the Pc, im just a regular 14 year old boy.
Also, sure, i have to study, alot, im getting close to GCSE's, but this does not stop my Playing games on and offline for 7 or 8 hours a day, i get my revision done, i get my homework done, im still an A - A* student, and everyone i know in my class has a 360 or tPS3 too, fact is, Gaming stimulates the mind, and makes you smarter, all the dumber kids never had a games console until they were 10 or 11, i started at 5, like most of my friends.
Also, dont bother trying to stop him, one of the best 4 months of my life was hacking into a friends wireless network his dad had completely locked down, the challenge of it, the taste of success when MSN finally signed in, the crushing blow when it was all locked down again. By the end of the 4th month he gave up, we had cracked, hacked and shutdown the network about 30 times, all so we could talk on MSN and Game on PS3.
My advice, leave everything unblocked, but keep checking up on him, walk in and clean up abit, every time you do it, increases the risk when he's looking at porn, and eventually you will start catching him quickly closing windows etc, this is when you will have cured it, the risk will have gotten too high.
My other advice would be buy a new Router, allow him ethernet connection, but get one with Parental Controls, change the username and password needed to get into the settings (192.169.0.1 - admin - password ? by any chance

) and using parental controls, you can monitor websites visited, block any sites you dont like, and set it to block all info in and out at certain times.
Im telling you this all from experience, I won my battle, will you win yours? For your sons sake, i hope not...