So the goal of the game is to pass classes until you get alchemist. Every fail, you have to retry your class, yes? But when you get to Alchemist, you reset everyone back to feeder, so you have to retry feeder.
An alchemist passing is literally the ultimate troll. You gain nothing, pass through six doors, only to make everyone have to retry feeder. You fail so hard that everyone is reset.
Hence Sixth Door Fail.
