Iruka sighed in annoyance as an invading Sound-nin mocked him. He only raised an eyebrow in amusement.
Konoha was the only Village who's Academy instructors were Chunin. The others all had Jonin assigned to teach the Academy students in shifts, while here, the Academy Chunin were more or less there to stay once assigned there. Sure, they still took the occasional B-rank, and they still trained to keep up their skills, but they didn't really leave the village a whole lot anymore.
What none of the other villages seemed to realize (in their mocking and scorn) was that the Academy was one of the most vital and important parts of the villages structure. It was where future shinobi were trained. It housed the future of their Village. If something were to happen to the Academy students, the Village would be left crippled for years as they scrambled to find enough new recruits to fit even one Academy class, shove them through the years of training in as little time possible while still making sure they had the necessary skill to at least survive as long as possible while taking as many of the enemy with them, and take some of the strain off the already established shinobi of the Village.
The new Genin, and even the students themselves sometimes, were relied on to run the 'errand-missions', the D-rank and the low C-rank that, while not really being shinobi work, still brought money into the Village and helped provide a bit of field training.
If something happened to the Academy students, the Shinobi force of the Village would get older and more worn out by the lifestyle without any fresh blood to replace them when they should retire. The Academy students were the Village's future, their safety ensured the continued existence of the Village.
So, why, then, would Konoha put Chunin in charge of the most important and should-be protected parts of the Village?
To put it simply, they didn't.
On paper, yeah, sure. They were all Chunin, they got paid Chunin salaries, they had Chunin levels of skill, and they clearly couldn't hack it out in the world. Why else would they spend their lives teaching a bunch of brats instead of taking missions and earning money?
In real life, however... there wasn't a single shinobi in the Village who didn't cower or jump at the Academy Chunin's command.
Before being accepted as teachers at the Academy, they were put through extensive training with the Jonin, ANBU Hunter-nin, trap masters, and the Nara clan. That was on top of a few classes taught by a few of the Civilian teachers about teaching in general.
They were taught how to recognize threats before the threat even knew they were a threat yet. They were taught every major Taijutsu style out there and ways to counter it. How to recognize and set traps behind them while guarding (re:herding) children (scared and panicking) where they needed to go to reach safety. They were taught how to rely on all of their senses and track somebody who may have taken one of their students. They were taught extensive tactics and strategy.
By the time they were accepted as Academy Chunin, they were fully capable of going S-rank missions solo.
They didn't, though.
They stayed at the Academy. Their skills were tested and honed every day by the students they taught. Spotting and disabling prank traps, hunting down and dragging students back to class when they run out or skip school that day, unexpected and surprising Taijutsu moves during sparring practice that should not have happened or worked, but they did. They knew when a student was planning a prank (or worse) as soon as the student started planning it.
All those skills they were taught in order to defend and protect their students? Paled in comparison to their biggest defense.
Enemy villages didn't expect a lowly Chunin, who couldn't cut it in the field, to be able to out-fight, out-smart, and best any Elite Jonin as if it were a walk in the park.
They didn't expect the Academy Chunin to be the true Elites of the Village.
"You shouldn't underestimate an Academy Instructor." Iruka merely informed his opponent before putting a Kunai in his heart and taking off to follow his students towards the evacuation point, setting traps behind him as he went.
And they never would.