'...since men who feel hate and fear also admire these emotions and wish to perpetuate them, although this admiration and wish will probably be unconscious...An education designed to eliminate fear is by no means difficult to create. It is only necessary to treat a child with kindness, put him into an environment where initiate is possible without disastrous results and to save him from contact with adults who have irrational terrors...A child must not be subject to severe punishments, or threats, or to grave and excessive reproof.'
-Bertrand Russell.

This may provide part of the answer to the question: 'Why, when everyone leaves school knowing exactly whats crap about it and exactly how to make it better, do they immediately forget as soon as they become 'adults' and become its biggest advocates?'

The answer is that an education filled with fear and hate will make you respect fear and hate and wish to inflict it on others, ideally ones who can't do anything about it because they are legally obliged to sit their and let you.