First off, check with your school's IT department.
- They might have a solution
- What you are attempting to do might violate school policy. You dont want to get suspended, right?
Now on to possible solutions. I find it hard to believe they are blocking your router. Is is possible, but unlikely. Plug the router into the dorm's ethernet and power cycle it and leave it there overnight. Without getting to technical, the switch/router at the other end is checking to see if the MAC has changed, which could be a security concern. If it doesnt work, then they might be filtering MAC addresses. Again, this would be a major hassle in a large university, so I doubt this is the case. If it still doesnt work, most home routers will allow you to change their MAC address. It sounds like your computer works, so you could put that MAC in your router, and it would work.
If that still doesnt work, you can always add another ethernet adapter to your PC and then bridge that with the port to the wall. Then you could hook your router to that and your Pis to the router.
Again, ask your school first. They will offer the best solution, if there is one.