Samer sed: "IMO, pre-establishing the brackets in
such a situation is inherently unfair because it means
that certain teams are at risk of being forced to play
one another, while other teams are not. Seeding teams
numerically, or doing a random draw for bracket pairings, is
far preferable."
However, a hybrid approach
seems to work well -- place multiple teams from one
school away from each other and then have everyone else
do random draws for the remaining spots. This is how
my old HS's tournament is run and there seem to have
been no complaints on this front.