Originally posted by: Shippou-sama
I first thought he joined early, but in all the flashbacks, he was still in the same group of kids as he is now. Also, if he had failed multiple times, but graduated the year he was supposed to (when all the other students were nearly the same age), then he probably wouldn't have been called such an idiot (not that they wouldn't have called him one, it just wouldn't have been as big of a deal).

I can't really figure it out either, as for the first few episodes, I thought he was 3 years older than all the other genins. So far it seems like you just take it more than once a year.

Or maybe the author just doesn't care.
if u cud take it more than onces per year dont u think sasuke and sakura would've passed first time? they're both extremely good at studies it showed that sasuke was #1 in the finals and we kno sakura is really smart