Windows 7: Force DNS server settings on a router/computer

So i have open DNS setup on my home router which is connected to my Verizon router (piece of crap) which i also have running open DNS. I run open dns for security and for filtering i have several teenagers in the house and i need to filter content. The only problem is that they can bypass the DNS server settings by setting them manually on there computer Start > Control panel > network and sharing > adapter setting > left click on adapter > properties > IPV4 properties and then change the DNS. I was wondering if there was a way to make it so this trick does not work? I have tried everything i know to do. I have set the open DNS, as the DNS server on every connection on my Verizon router and on my linksys router but it can still be bypassed. How can i fix this?

Thanks

Put a password on all admin accounts. Let the kids run the computer as a "standard user" account. A standard user cannot change those settings unless they know the admin password.

You can do most of this stuff using the GPO "group policy editor".

You can set up standard user accounts for all clients in the GPO, then use the DNS settings in the GPO to define which DNS servers can be used.