One good way is look up a picture of broken screens and set it the background photo, screensaver, or just pull up the photo on full screen to make it look convincing that the computer’s screen looks cracked and broken. If getting the computers dirty gets Mrs.Beverley mad, convincing her that you may have broken the computer will get her furious.
You do want to make a scene and give off the impression of you breaking it such as a fight. Having you and another student pretend to argue to and make a huge sound such as throwing a chair on the ground to give off the illusion of you guys breaking the computer.
WHAT DID YO DO!
Of course, if you want to see her true reaction, you could always actually break one of the computers.