I remember reading it and enjoying it back in junior high school, but I don't even remember anything about the story other than the title. Maybe time for a re-read.
I'm going to play devil's advocate here. What if everyone is already smart? People tend to define smartness according to what's important to them, maybe what they're particularly good at, or maybe by the things they find particularly challenging. Both are self-serving definitions. The first lets the person elevate their own smartness standing, while the latter allows them to excuse ignorance of something as acceptable because they've elevated it to a category achievable only by a super genius.
So, while folks are tossing around being able to build a nuclear reactor as a level of smartness, what if we changed the requirement a bit and defined it as being able to build a house, or fix a car, or operate construction equipment? Or, what about being good at gaming the system to get free meals and shelter while sitting around all day not working? (My cat seems really smart in terms of communicating her demands for food and a warm lap to sleep on when she wants it.) If we more broadly define smart as being able to acquire a skill set that enables one to obtain all of the essentials for survival, very few people would fall into the stupid category.