Warning! Spoilers ahead for My Hero Academia chapter 323!
My Hero Academia has already revealed that U.A. High protects those sheltering there with a state-of-the-art defensive system. But the latest chapter goes into further detail when Principal Nezu explains how he actually transformed the school into a giant robot. In fact, when Nezu divulges all of the modifications that he invested into U.A., class 1-A student Denki Kaminari is so impressed that he references Neon Genesis Evangelion by exclaiming, "What is this, Tokyo 3?"
While the whole robot thing might seem like overkill, it's not. All For One recently took over the body of his apprentice, Tomura Shigaraki, who underwent an experiment to awaken his true powers, so Nezu's school definitely needs a high-performing defense system. There is also the chance that Deku could return to U.A. High after he left to protect his classmates and everyone around him, and since All For One is specifically looking for the young boy to acquire his One For All quirk, Deku coming back would greatly increase the likelihood of the school getting attacked.
First revealed in chapter 323, the most robotic-like upgrade comes to U.A. High via elevation facilities that were installed into various sectioned-off areas of campus to allow the school to move underground during an emergency. These sectioned parts can then be transported and scrambled about further to minimize detection through a complex series of underground tunnels. Additionally, around 3,000 steel-enforced plates of armor surround the perimeter of the school, so when any breakage occurs on the surface level, it will automatically trigger an emergency response. Nezu sought to minimize the possibility of decay in this instance by partitioning each plate from each other.
The latest chapter confirms what Toru Hagakure aka Invisible Girl alluded to earlier about U.A. and Shiketsu High being connected before she was rudely interrupted. This is a big deal since they are located on opposite ends of Japan. Ironically, Nezu's confirmation of Invisible Girl's earlier comment doesn't provide any specifications as to how the campuses are ostensibly connected, though, it's possible that the aforementioned interconnected tunneling network that scrambles each section of the school reaches Shiketsu as well.
Suffice it to say, these extensive upgrades further underscore what readers learned about U.A.'s defensive capabilities in the previous chapter, when it was revealed that the school became an impregnable fortress, with high metal walls that will most likely render frontal assaults from the ground irrelevant. Hopefully future issues of My Hero Academia will allow readers to witness these modifications in action during an actual assault. These brief explanations undoubtedly serve as a means to whet the appetites of voracious readers who love all things mecha, but it would be a shame if they only act as a replacement for a true demonstration. Regardless, the fact that U.A. High is now essentially a robot changes the desired outcome of Deku not being allowed back to U.A. High to keep future developments more intriguing. Hopefully, Deku will return so All For One targets U.A. High, forcing Nezu to trigger the school's defensive response. One question still remains: are there offensive capabilities? The answer may be revealed in upcoming chapters of My Hero Academia.