Without using squeel, default scope with sorting inherited to STI sub class

test.rb

# encoding: utf-8

gem 'sqlite3', '1.3.6'
gem 'activerecord', '3.2.8'

require 'active_record'

require 'logger'

puts "Active Record #{ActiveRecord::VERSION::STRING}"

ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Base.establish_connection(
  :adapter  => 'sqlite3',
  :database => ':memory:'
)

ActiveRecord::Schema.define do

  create_table :customers do |t|
    t.string :name
    t.string :type
    t.datetime :start_at
  end

end

class Customer < ActiveRecord::Base
  default_scope order( :start_at )
end
class Company < Customer; end

Company.last