default_scope.md

On your assignment:

Because you have a default_scope the other scopes that you created will all be affected by it. Therefore in order to get the right order in your other scopes and ignore the default scope you need to use reorder

default_scope { order('created_at DESC') }
scope :ordered_by_title, -> { reorder('title ASC')}
scope :ordered_by_reverse_created_at, -> { reorder('created_at ASC') }

Also, check out the unscoped method for removing the default_scope in any situation.

http://apidock.com/rails/ActiveRecord/Base/unscoped/class

http://apidock.com/rails/ActiveRecord/QueryMethods/reorder