The Harry Potter world and the Naruto world actually have a ton of similarities, despite one being British and the other Japanese. Both start with young teens going to a special school where they learn magic-like skills. Near the beginning of both series a rogue teacher draws the main character into a dangerous confrontation over a valuable artifact that the rogue wants to steal. Then the main character becomes part of a 3-person group that alternately squabbles and works together tackling various adventures, missions, and opponents. They are constrained by their low rank/not being recognized as adults, and have to compete to earn certifications to make progress towards becoming full-fledged warriors considered as equals by their teachers. Destiny is shown through information about the main character's dead parents and a prophecy. And so on.
I'm thinking about inventing a new world of this general type. Right now I'm trying to figure out what kind of special ability the main characters should be trained in, why this school exists, what kind of tests they should have to go through (probably a tournament, but what kind, and held by who), and who the enemy actually is. I don't want to have any explicitly supernatural elements - no ghosts, vampires, demons, or gods. (Edit: This means I really don't want to do the prophecy thing that both examples did.) Magic is ok, as long as it is presented as either a natural part of the laws of physics of a fantasy world, or natural biological abilities of a non-human race. I'm not sure I want to have elements be involved, and definitely not good vs. evil. I want to have a more explicit process of specialization, where the teens have to decide what role they want to specialize in, then earn it, and there would be some kind of irreversible metamorphosis. The end result should be an almost insect-like social structure where the group as a whole is the reproductive unit; no nuclear families. Similarly, individuals would usually not have jobs in some kind of capitalistic system, but instead the group as a whole would be an economic unit.
So, what's the actual question of this thread? Well, two things: What do you all think is good or important to include in such a world's design? And, do you want to recommend any similar series as research material? I'm aware that jedi in the Star Wars universe are kind of like ninja, but I never liked the philosophy or culture of the Star Wars universe much; I see jedi as being like paladins or clerics, and I strongly dislike religious warriors or mages. The anime series Bleach similarly has shinigami who are like ninja, but although there is a shinigami school, the main character doesn't attend it, and he doesn't really act as part of a team either.