|Sorry for taking so long to reply. I'm the worst procrastinator in the world.
Also, you're the first person ever to request a review from me. So thank you for that.
Your wanted to know if this story is worth continuing. Short answer: yes, very much so. Long answer:
Two things immediately jump out at me. One, the story needs reformatting. There should be a line break after each paragraph...
...like this, see? I know most printed works use indents rather than line breaks, but when posting online, that approach just winds up with a big wall of text that's really hard to read. It's not that tricky a fix, though it might take a few minutes. Two, you need to bump up your rating, to at least '13+' if not '18+'. The climactic fight is enough to warrant it, I assure you. 'E' is the equivalent of, like, Disney movies, and how many of those include a guy being beaten into a coma?
But that's the only major issues I can note. Otherwise, it's all positive, you'll be pleased to know.
'Utopia with a dark secret' is a theme as old as time, but it's one that always produces good results. We all dream of heaven in some form, the pearly gates or seventy-two virgins or oneness with the cosmos or whatever, and allowing dark shadows to creep into that fantasy brings with it an inherent menace. The society of the Pyramid certainly lives up to that potential, and even adds some interesting twists to the formula. I really like how...self-aware, I guess that's the right world, it all is: the citizens know that every day of their lives is controlled from above, they know that they're being medicated into being happy, and at the same time they're completely okay with it. The disconnect between the two things is wonderfully creepy.
Also, the Oracle and her minions have been presented in a clever way. They seem to genuinely love the people they rule over, not just desiring "what's best" in the way that we might care for a slightly dumb pet, but taking a deep, personal interest in ensuring that every last individual is happy and contented. The fact that, like the more disinterested tyrants of dystopian fiction, they still show this love through mood pills and social conditioning...it just makes them that much more disturbing. When manifested in the wrong way, love can cause even more pain than hate.
(One question, though: why have the Genteels never dealt with Darrius? I've never considered throwing spitballs to be the sign of a happy mind. Maybe you've written him that way on purpose, I don't know, but some clarification on that point might be useful.)
Jackson and Andrew are an interesting pair of lead characters. One a misfit, failing to blend in both physically and emotionally, the other more "conventional" but still beginning to question the world he lives in. Again, these are familiar archetypes, but you've started building on them effectively, making the pair feel like rounded people even as we still know little about them. I don't know how you intend to develop them from here, though I have every faith you'll make it worthwhile.
In terms of the technical details - grammar, vocabulary, syntax - there's nothing major to comment on. Prose leans towards the purple at times, but your main character is a teenaged boy filled with emotions he literally can't control, so that's precisely what it should be doing. I will note, however, that there's a few points, especially towards the end, where you abruptly change viewpoints between Jackson and Andrew. It's kinda confusing, and I reccomend just sticking to one viewpoint per scene: how you make that work, I leave up to you. Also, and I'll admit this is really minor point, you might want to find ways of describing a person's figure other than with the word 'frame'. Once is okay, but that kind of repetition can get annoying. Granted, it's tricky to find enough synonyms without reading like you chewed up a thesaurus, but see what you can do. Like I said, a minor point.
(Truthfully, if you want some proper feedback on the technicals, you may want to find someone else to ask. So long as a story is comprehensible on at least a basic level, I've never really cared. Concepts have always been more important to me than presentation. You could've written the whole thing in street slang, and it wouldn't make any great difference to me. It worked wonders for Anthony Burgess, after all. Anyway...my point is, all I told you was what little jumped out at me. There's probably a bunch of good and bad things that I've missed.)
As to the plot, it's not clear what direction that's going to lead, but what you've got still looks promising. Though I am wondering one thing: where in the wider novel is this section going to be placed? The opening, I'm guessing, but to me it feels more like a condensed version of the entire first act. We need more scenes in the UnderSchool, and Jackson and Andrew's relationships with the other students, before we get to an event as cataclysmic as Darrius' death (unless it turns out he survived, which looks unlikely). The more time you can spend building up tension for an event like that, the better.
Relatedly, a lot of the world-building you've done already can wait until later in the novel. In these kinds of stories, exposition needs to be drip-fed: dealing out tiniest morsels of detail about the Pyramid, about its workings and backstory and place in the wider world, with each piece only coming when immediately relevant to the scene at hand. The more work your audience has to do in understanding the setting and its nature, the more immersive it will feel.
(I know I said it was going to be all postive, but please don't take the above as a criticism. What you've got so far works in its own right, there's simply ways to take it further.)
And that, I think, is all that I've got to say for now. Still a lot to take on board, perhaps. Hopefully I've been of use.