So there's this story I've been wanting to write since at least 2006. The basic plot is similar to another story I recently found. It's about a war but young kids are made to get involved, like the series Animorphs (it's kind of fantasy like Animorphs too, it's not very realistic). So, is there anyway I can learn to write this kind of subject other than reading Animorphs and going through the tv tropes page?
Just tell your own story here. And do not pay attention to what may have been written previously. Anyway, that's what I would do. Sometimes later, AFTER you have finished the nuts-and-boots you can read it/watch tv tropes, but first you have to have a baseline on your own. Otherwise you may unconsciously rewrite everything which is out there already. My 5c
I'm with @Lifeline. I actively avoid reading in my genre when I'm writing, or preparing to write, or I unconsciously mimic something I've just read. Anyway your plot is only similar to Animorphs in its most basic terms.
Well, I'm going to be brutally honest. Children or teenagers getting involved in adult roles is an immediate red flag for me. Even good stuff in that area is not as good to me simply because of that. It's just unrealistic, and it can make me feel annoyed at various points in the story, especially given the things it tends to come with (angst, bad romance, some kind of slightly lame sci-fi/fantasy plot often with simplistic villains.) But I don't think you should stop reading stuff. Ideas that are similar to others things will occur anyway. And there's only so much you can worry about that. Stay vigilant but remember there is no such thing as a mind-blowingly original story. There will be elements of trope. Tropes are fine. They're just categories for trends.
Sorry, but there are happenings right now where children assume the role of adults. Look at child-soldiers. Or children made to work like men. I am not saying that in this genre that is commonplace, but these things happen right now.
Yeah, in completely inhuman fucked-up situations. Not like in Harry Potter and stuff, where's the no realistic explanation for not employing mostly or entirely adults. ( Screaming at screen) "Let adults do the dangerous stuff, you're supposed to live so you can be the next fucking generation! You literally could have got someone else better to do it! Harry; tell goddamn Dumbledore about the goddamn snake!! Are you kidding me; the only adult you take is the Mr Magic-Away-Your-Bones the Dickhead?! Oh my god!!! This is not ethical! Let Snape deal with it! He's Alan Rickman he could probably scowl it to death nevermind your shitty arse fighting! Hogwarts needs new fucking management rules why do they never get punished for this shit?! Oh, and then Dumbledore decides he should actually encourage it!! I have hundreds of well-trained experienced adults to fight for the cause but what I really need is an army of barely competent teenagers!!!" I didn't actually rant like that, but I should have.