block itunes.apple.com

I teach in a secure care setting school. I've used student accounts and parental controls to set up and block almost everything. I can use a third party product to block more web traffic, but I have to be at my workstation with the product running. We use Safari and the apple dictionary app regularly in school.

I still have students who are able to find music links using the dictionary app. I cannot turn off the wikipedia option in the dictionary permanently.

I have set up a whitelist using parental controls, but for some reason it does not block "iTunes.apple.com"

Is there any way to 1) block "iTunes.apple.com" in safari, and 2) is there any way to turn off the wikipedia option in the dictionary app?