In Twitter Bootstrap 2, how can I get right columns to move to the top when shrinking the screen?

In bootstrap 3 this is done with grid column ordering
(see bootstrap 3 documentation)

Example

<div class="row">
   <div class="col-md-9 col-md-push-3">.col-md-9 .col-md-push-3</div>
   <div class="col-md-3 col-md-pull-9">.col-md-3 .col-md-pull-9</div>
</div>

This will show the upper div behind the lower div if there is enough space. If the screen size is reduced the upper div will stay up.