Jack is right.
While most routers will allow you to block specific addresses, this doesn't amount to a practical parental control capability. How will you manage to identify all the addresses for sites that parents don't want their kids to see, and how do you keep that list updated?
The parental control packages I'm familiar with (like Norton Internet Security) rely on regularly updated lists of addresses downloaded from the vendor site. These are characterized by content, so that the adminstrator can tailor access for each user account. Besides the obvious porn blocking, parents might not want their kids surfing through satanic rituals, racial intolerance, gambling, violence, etc. On the other hand, the parents probably want the option of surfing without restrictions. Easy to set up in Norton; not so easy if you have to alter router settings. Figure on paying about $40/year for the updated address lists and software updates.
Good luck!
