Hi sabina27& kris.boylan!
The badges or missions that have the same action are actually for posting them in specific spaces. For instance, "Class President" is listed on page 3 of the Missions and is surrounded by mostly High School related missions. In that instance the mission is achieved when 100 of your posts are marked as correct in the HS space.
I personally never liked the missions/badges that didn't list specifically how they are achieved, as I think it's confusing. Not to mention there are so many that seem to be repeats, even though as I just explained they aren't. But it sure looks that way.
Hope this helps!!