Missed the edit, but just to add 'keep-away' is 'piggy-in-the-middle' in the UK, and I don't know if perhaps you have it too but 'swingball' is a similar game to 'tetherball' but played with a tennis ball & (typically not tennis, but just cheap plastic thing for the purpose) racket.
I didn't know and wouldn't have guessed there were world championships, though.