Facts vs Fiction

Just how much of this movie was based on true happenings? For example - the opening scene fracas, the Elston (janitor) character, the girl swimmer (Willie), the first contest where the PDR team gets whipped by the white team, the aftermath (PDR team tries to laugh it off, Jim delivers The Lecture, PDR team then turns over a new leaf), the second no-contest where the white team pleads illness, and of course the third contest where the PDR team emerges victorious and carts away The Trophy. Which parts were based on factual events, and which on fiction? Does anybody out there know? If so, please share.