story.rb

class Story < ActiveRecord::Base
  
  has_many :story_keywords, order: "score DESC", dependent: :destroy
  has_many :keywords, through: :story_keywords, order: "story_keywords.score DESC"

  def keywords
    super.merge(StoryKeyword.stanford)
  end

end

story_keyword.rb

class StoryKeyword < ActiveRecord::Base
  belongs_to :keyword
  belongs_to :story

  def self.stanford
    where(source: "stanford")
  end

end