How to stop openDNS bypassing?

[deadboy000]

So I've setup openDNS through the router, but kids change the local DNS on their computers which completely bypasses all the settings. I was reading this article https://support.opendns.com/hc/en-us/articles/227988027-How-to-prevent-users-from-circumventing-OpenDNS-using-firewall-rules but my router doesn't have any firewall or port blocking options. What it does have is port forward, there's blank spaces for internal port and external port. It also says about doing it on windows firewall on a computer that is at the edge of a network, I don't even know what that means and don't see any router options for it. I'm using Bell 3000 router. It has an access control page but all it does is completely kill off the internet which isn't an ideal option.

Thanks for reading. 

[rotblitz]

If your router does not allow to configure outbound firewall rules, you supply regular user accounts for your users, not admin accounts, and you configure the computers' network settings to obtain them automatically via DHCP from the router.  Regular user accounts cannot change the network settings and cannot install most VPN clients which is another favored way to circumvent restrictions.

"doing it on windows firewall on a computer... don't see any router options for it."

The Windows firewall is on the computer, of course, not on the router.  But even if you use the Windows firewall for this, admin users can change it again, same as the network settings.  So it stays with that you supply only regular user accounts for your users.