I also forgot to mention that when people hard-code the speed and duplex, 9 out of 10 instances I saw, the interface readings/counters get HIDDEN. When the speed and duplex settings get hard-coded, theres a significant chance you'll generate speed and duplex mismatch errors and counter. These counters tend to hide more serious stuff. It's like "self-inflicted injury" when troubleshooting potential NIC or cable issue. Because of the "self-inflicted injury" caused by hard-coded speed/duplex settings, you tend to NOT see what other problem exist.
So here's how you do this:
1. DO NOT enable the ports yet;
2. Clear the interface counters: clear count <port>;
3. Clear the controller counters: clear controller e <port>; and
4. Enable the ports.
Finally, a workable solution to your initial problem: How to slow down the student network traffic. You use a system called traffic-shaping. Configuration guide can be found HERE. By the way, use traffic-SHAPING and try to avoid traffic-POLICING.
Another thing: When you've enabled the ports, keep them under observation for a few more days or until they've gone into error-disable again. When this happens let us know. Can you also specify the exact model number of your switch and the IOS version it's running on. We may need to know this information before the next time the ports go into error-disable.
