class School < ActiveRecord::Base
	include PgSearch
	multisearchable :against => [:dbn, :school]
	pg_search_scope :search_schools, 
									:against => [:dbn, :school], 
									:using => {
                    :tsearch => {:prefix => true}
                  }
end

class School < ActiveRecord::Base
	include PgSearch
	pg_search_scope :search_schools, 
									:against => [[:district_code, 'B'],[:district_name, 'C'], [:school, 'A']], 
									:using => {
                    :tsearch => {:prefix => true},
                  }
end

Modify pg search scope method to take one more field
Modify pg search scope method to take one more field
