Who says Jack can’t play and learn at the same time? Suppose balls and bats and hockey sticks were covered with vocabulary words. With definitions, of course. Casually, those words would work their ways into minds and conversations. Heck, maybe cover a whole playground with words, names and ideas worth learning. Those in some jokes for comic relief. Beats covering everything with advertising. (Although if sponsors want to insinuate their names in exchange for providing cheap or free equipment, why not?)