How does the setting of the Battle School affect the conflict in Ender's Game?

The Battle School is constructed for the sole purpose of
training children to fight in outer space. The children are not coddled or protected,
but allowed to fight among themselves. The teachers deliberately set up the rules to pit
the children against each other, in order to teach them strength of character and to see
how they react.

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"...you will get pushed around. And when you do,
don't come crying to me. Got it? This is Battle School, not nursery school... If you
don't like getting pushed around, figure out for yourself what to do about
it..."
(Card, Ender's Game, Google
Books)

Battle School is
isolated and far from parents. The only authority figures are more interested in seeing
how the children adapt than in protecting them, and so the children who don't get
expelled become hard and cynical. Ender avoids cynicism for the most part, but the
constant brutality makes him very pragmatic, which sometimes comes across in violence.
Without the Battle School, which taught persistence through adversity through never
playing fair, Ender would never have learned the lessons and the determination necessary
to win the Bugger War.