There are websites which will corrupt your file for you, or even generate a file of gibberish that you can name appropriately, so that you can appear to submit your homework on time, but actually get more time to work on it. When the teacher gets around to reading your work a couple of days after the deadline, Word or whatever cannot open the file, so she sends you a message and you reply "Sorry, miss" and immediately supply a new file of the same name, which is the homework that you actually completed after the deadline.
Mind. Blown.