In the original book, both Naruto and Sasuke graduated from ninja school at the age of 12.

Not to mention the unclear study years and time in the original book, just the introduction of Naruto's repeated grades a few times must make me advance Naruto's study time.

And the extermination of the Uchiha clan was when Sasuke was about seven years old, so my arrangement was that Sasuke was going to enter the graduation assessment class, but because of the extermination of the clan, he recuperated at home for a few years, and then graduated with Naruto, so it would make sense.

As for why the study in the Konoha Ninja School is six years, hey! Let me reminisce about my elementary school......