Originally Posted by Unruly_Saiyajin

Have you ever thought that there could be more than 1 academy? For example in our world we do not have one school for every county...
Konoha is the only Shinobi Village in the Fire Country. It only has one academy.

Also, consider that there are multiple classes of students being taught. I mean in our world do we have just one big classroom?
Back in the 1700 - 1800s. But regardless of that, look down.

One more thing. How do we know only those 9 Genin graduated. There were a lot of other students there as well. The story only focuses on these specific teams, I'm sure there are more.
Kakashi stated only nine would pass. Only 9. Out of everyone who graduated.