Action to change role?

Is there an action that can be triggered to change a user's role?

I expected it to be part of Drupal core, but I didn't see a way to add it. I tried looking for a module that would enable that functionality, but there don't appear to be any. Surely this is something that would be useful. When something like this has happened in the past, it's meant that I'm going about this the wrong way, and there's a good reason why you shouldn't do it this way... so let me explain what I'm trying to do.

I want to restrict the users who can edit a content type to only those who have proven that they aren't stupid and know how to type correctly. The only way I could think of doing this passively (without one on one interaction with me) was to create a test using the quiz module. The quiz module can perform an action upon passing a test, so I intended to grant a particular role to the user which would allow them to edit the content type.

Is there a better way to do this? Should I try writing a module for this myself?

Thanks in advance!