On the computer lab computers, 8086's, it would take several seconds if not minutes to render on the screen, one line at a time. That gave everyone plenty of time to escape out in case a teacher or someone else walked by. And there was only sky and trees and stuff mostly on the screen at that point.
Later on, a year or so later, the typing teacher got a 6 new computers, 386s. The first kid to try them out to look at the bathing suit pictures found that the images rendered instantly and completely. He was so stunned by seeing the entire image way sooner than he expected, but also, I guess, seeing the entire image itself. He let out a "Oh shit!" which caused the teacher to turn around and see the contraband on the screen.
Student had his disk confiscated and was banned from using the school's computers for the rest of the year.
Times were simpler then.