Provide a more consistent and better way of selecting and deselecting all items in a list

I see Select all / Deselect all controls as buttons/button-groups on other pages and links on others (e.g. mod_choice, mod_lesson). It might be better to make these consistent. I vote for these to be rendered as buttons since they act like buttons which are meant to perform actions.

Update:
From the discussions below, a check all/none checkbox would be a better way to improve the select all/none functionality.