There was an ongoing competition in 2nd grade relating to who would walk down to the lunch room next to the cool kid when the teacher led us there in pairs. Why was he cool? Because he was a little older then us, and so qualified for the cub scouts before the rest of us. That same kid also earned his 2nd grade cool qualifications because he owned a pet duck.
There were other ways to be considered cool. There was the kid who could reverse his eyelids (gross is cool). I learned in first grade how cool pop culture was when I brought to school a stack of 8x10 photos from the "Batman" movie that my dad had brought home. I took out the photos - and instantly had a crowd around me! Cool. If I had been asked about what was cool about some of my friends, I would have mentioned one kid's St. Bernard, another kid's gas-powered RC Car (okay, that's still cool), another kid who had shown me his dads World War 2 uniform deep in the basement, and another kid who had been in the audience on the most popular kid's TV show in the New York area ("Wonderama" - yes, that was very cool).
Cool, though, wasn't a set concept. If you weren't within a year or so in age, you wouldn't be considered cool. A kid about four years younger then the rest of us whose father was a movie producer - uncool. If he were our age - cool. Of course, how easily one defined coolness changed and became more difficult with age. In junior high school, another kid whose father was producer of a popular TV show was sometimes seen as uncool just because of that fact. At that age, eyelid reversing would have been extremely uncool. RC Cars would still be cool, though.