i mean, it's hilariously bizarre:

In other anime, kids go save the world in their lower teen years. Here the heroes are supposedly adult (lol) and still go to school in season 606050040.

What's really bad, however, ist that they already fought the most dangerous villains - what's left to learn at school? Learning about rules etc. shouldn't take long, and combat ability improves during your work as a hero and your spare time. So, literally, what's the purpose of going to school for so many years?