*Laugh* I genuinely hope that you are not serious with this. If you are not, then I thank you for the good quick laugh I had, but if you are...well...then...it seems that you simply need to take a deep breath, find your calm and happy place and then totally review what you just asked, and you will slowly begin to realize why I am laughing.
If all else has failed, then...unplug your sons computer...or, simply call KI customer service and set up an appointment to have one of their employees come to your home and unplug it for you.
That's right! LOL! KI will allow you to control whether or not your child is allowed to use Menu Chat, Filtered Chat, or Open Chat. You will allow you to control how much time your child spends on the computer. But if you are completely serious about this then I do have a legitimate solution. Get some software (similar to Net Nanny - but I must say I don't know which one exactly. You will have to search around for something that will work.) that will Allow / Disallow internet usage during certain times. Install that on his machine and then lock down his internet access time. If he cannot access the internet then he cannot access Wizard101. If you have some technical knowledge then you may be able to do this through your router as well but that is a much bigger headache.
If you have Windows Vista, you can set this up on the user account level.
I believe it lets you limit the amount of time a person can use a program. For this to work, you need to set the kids accounts to non-administrator and have passwords set on the administrator accounts.
We had to do this with Battle for Middle Earth with my son. It's been so long I don't remember the exact steps to take.