I'm glad you found it useful. I have 3 boys, oldest being 8. The approach you're taking is dead on. My kids will not have a computer in their room either.
Because my kids are so young, I haven't tested K9 against the rigors of a 9th grader. Kids are darn clever these days, He/She may be able to bypass it. Another reason to not have the computer in the room
That's the FIRST step to protecting your children from the SCUM of the net. It's just to easy to get lulled into a sense of security. These scum-balls are SMART and good at what they do. Keep the computer in a FAMILY area where everyone can "Enjoy" it. Even a laptop doesn't need INTERNET access upstairs in the kid's room