There is no such method in ActiveRecord::Migration to alter scheme name, but you able to use plain sql command.

First generate migration file:

$> bundle exec rails g migration RenameSchema

Then open it and add:

class RenameSchema < ActiveRecord::Migration
  def up
    execute "ALTER SCHEMA you_old_name RENAME TO you_new_name" 
  end

  def down
    execute "ALTER SCHEMA you_new_name RENAME TO you_old_name" 
  end
end

With that migration you can change name and rollback it back.

_{Note: You must own the schema to use ALTER SCHEMA. To rename a schema you must also have the CREATE privilege for the database.}