I was banned from the computer labs at my high school for a year because I did this. Setup a timer so it would start after school got out, when the Adult Education class was going. They were learning how to use a web browser and click on links. I watched through the window. Every two seconds another monitor turned blue, in sequence, down each row. I could see fear and panic as the wave of unknown computer behavior moved through the room. Some of them sat there. Some stood up as if they might need to run away. The ‘teacher’ was at a total loss.