In my day if you didn't pay attention you got a blackboard eraser thrown at you...

Wouldn't it be easier to change the settings on your proxy/firewall so that the machines are denied?

Even easier, remote kill any active IE processes. Do that in a loop that runs every 60 seconds and the pupils will soon get bored with restarting IE.

As an added bonus, the teacher can get a list of all the machines that it is running on so that persistant offenders can be more accurately targetted with the eraser.