I would be more inclined to think it may be an issue with your school's firewall that is not allowing outbound traffic on port 4125, which is what is being utilized to provide the Remote Desktop service through the web browser (Standard RDP uses port 3389, but the Remote Web Workplace that WHS utilizes uses 4125). It is quite possible your school is only allowing outgoing traffic on ports 80 and 443 (standard http and secure https).
Is the problem you're having just with the remote connection to your network computers or to the WHS remote access site in general? The remote access site won't require much bandwidth at all. Even the Remote Desktop session does not utilize a whole lot of bandwidth. I've measured bandwidth utilization of an RDP connection and it is typically only a few kbps, even a 56k dial-up modem should be able to handle it without too much issue.