Just off the top of my head, there are a number of ways to do it.<br/><br/>If you consider Avalanche to just be a school then someone could simply decide to dropout.  <-- probably the easiest reason to explain.<br/>People could also be kicked out.  Reasons could be "discovered proof of cheating on an exam", "lied on transcripts", "failed to pay tuition", "failed to turn in the required paperwork", etc.<br/><br/>If you consider that Avalanche is akin to Bootcamp or Seal training, or something like that, then the dropout reason would be the most prevalent.