My 2nd grade teacher accused me of "hacking" the Commodore 64 when she caught me showing another kid how to write a "what is your name" program. (Of course this same school unplugged all their C64s on Michelangelo Day so you can guess their level of tech training.)

I never did it at school but there was always the "fake prompt" trick. Do a few fun things -- throw up fake syntax errors (including transposing characters the user typed correctly) -- print out some rude error message or "formatting drive..." -- and then silently hand control back to the real shell.