WARNING: The following contains spoilers for My Hero Academia #306, by Kohei Horikoshi, Caleb Cook and John Hunt, available now in English from Viz Media.
Chapter #306 of My Hero Academia shakes things up in a big way with Izuku Midoriya leaving U.A. Though his exit was to protect the people sheltering there from the villains after One For All, the truth is that Deku has been drifting from U.A. for a while now. The training he underwent to be worthy of All Might's Quirk and his own wealth of hero knowledge already put him ahead of most of his classmates, but add in extra-curricular mentoring from Gran Torino, and it's clear that Deku wasn't long for the academy.
But he's not the only one. U.A. is home to the best and brightest of the next generation of heroes, which means there are bound to be more students who've outgrown or don't quite fit into the standardized education offered there. For one reason or another, certain U.A. students might benefit more from training and learning elsewhere.
Katsuki Bakugo, Who Needs A Tough Private Tutor
Katsuki Bakugo is a rather destabilizing element in class 1-A, due to his uncooperative attitude, extremely competitive ways and propensity for causing collateral damage (though he's working on that). Bakugo is at the top of his class, but he might make more progress if he had a teacher who was on his wavelength. His current homeroom teacher, Shota Aizawa, doesn't have much patience for Bakugo's attitude -- a sentiment shared by many of his teachers and peers. Or maybe they just don't understand him?
A good option for Bakugo might be a private tutor, someone able to handle whatever Bakugo dishes out, physically or otherwise. Bakugo having his own personal All Might could finally hone him into a hero, and give him enough personal attention to break him out of his worst habits. Bakugo's an energetic guy and needs someone who can focus his mental and physical energies -- and this someone isn't at U.A. Tough though U.A.'s faculty is, none of them are the drill instructor someone like Bakugo needs.
Koji Koda, Who Should Aim For A Different Career Path Anyway
This isn't to say that Koji Koda doesn't deserve to be at U.A., or that he is a failure as a trainee hero. Koji Koda has more than proven himself worthy of class 1-A, and being at U.A. has helped him come out of his shell as must as its helped him master his powers. However, while Koji's Anivoice Quirk has application in the hero world, his talents can be better used in another context.
Koji prefers the company of animals, and while he's no coward, he doesn't necessarily have the nerves of steel necessary for violent hero work in a world where the League of Villains is steadily growing more violent than ever. Instead, he could train to use his Anivoice Quirk in the civilian sector, where he wouldn't unnecessarily endanger himself or the animals he calls on. After all, it's not like Tomura Shigaraki will be defeated by a flock of pigeons.
Mirio Togata, Who Has Already Outgrown U.A.
Up to a point, Mirio Togata definitely needed everything that U.A. had to offer, and during that time, he learned to master his remarkable Permeation Quirk and established himself as one of U.A.'s Big Three. Thanks to all that hard work, though, Mirio is now a big fish in a small pond -- it may be time to move on.
Mirio has incredible potential as a hero, and he already outclasses many actual pro heroes. It helps that he has a lot of hands-on experience out in the field, but Mirio's skills are at the point where attending class at U.A. might be holding him back. Clearly, this third-year is ready to move on, primed and ready to dive right into the professional world, or at least, attend a few online classes and leave it at that. Mirio doesn't need homeroom; he needs to be out there, fighting real crime.
Pop Step, Who Thrives In The Public Eye
The My Hero Academia: Vigilantes spinoff features a few characters who became unlicensed, homegrown heroes. Among them is a young heroine called Pop Step. She has legitimate street smarts and is skilled with her Quirk, but she wouldn't get much from U.A. -- she probably wouldn't even qualify for class 1-A.
Pop Step thrives on attention, naming herself for the pop idol performances she loves. Pop Step enjoys putting on impromptu musical performances and is savvy with social media and organizing larger musical events -- she's a hero of the current age. U.A. can't help Pop Step with any of that; she can handle herself.
Mei Hatsume, Who Has Also Outgrown U.A.
The support student known as Mei Hatsume is arguably the best at what she does. Mei Hatsume is an expert in machines and devices, fondly calling them "babies," and her Zoom Quirk acts as a natural microscope. Mei has already built devices to aid Izuku Midoriya, Tenya Iida and even All Might himself (somewhat unsuccessfully in the latter case), and Mei can do more.
Mei could and probably should move on to professional research and development labs and workshops, and provide supplies for pro heroes and related figures. It should be pointed out that Mei is already looking for corporate sponsors and clout, and she can't get much of that while sequestered at U.A. This brilliant young woman is ready for the professional hero and everything it offers, and she can test her "babies" against many villains on the streets, not just against her fellow U.A. students.