being a cable installer this made me smile, school children seem to have a need to rip labels off the front of network sockets if there within range of there little hands,
if the cable is there, and is plugged into the switch - but there are no lights that would tell me there is nothing plugged in at the other end, or the cable has been broken.
test it with a simple set of cable testers, if you get all your lights then the socket works, if you dont get all your lights, unscrew the faceplate in the classroom and look to see if it looks like it has been pulled away from the cable, if so you will need to re-terminate the cable with a cat5e punch down tool (you can buy these from maplins)
q[^.^]p good luck